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Patch series "Per-VMA locks", v4. LWN article describing the feature: https://lwn.net/Articles/906852/ Per-vma locks idea that was discussed during SPF [1] discussion at LSF/MM last year [2], which concluded with suggestion that “a reader/writer semaphore could be put into the VMA itself; that would have the effect of using the VMA as a sort of range lock. There would still be contention at the VMA level, but it would be an improvement.” This patchset implements this suggested approach. When handling page faults we lookup the VMA that contains the faulting page under RCU protection and try to acquire its lock. If that fails we fall back to using mmap_lock, similar to how SPF handled this situation. One notable way the implementation deviates from the proposal is the way VMAs are read-locked. During some of mm updates, multiple VMAs need to be locked until the end of the update (e.g. vma_merge, split_vma, etc). Tracking all the locked VMAs, avoiding recursive locks, figuring out when it's safe to unlock previously locked VMAs would make the code more complex. So, instead of the usual lock/unlock pattern, the proposed solution marks a VMA as locked and provides an efficient way to: 1. Identify locked VMAs. 2. Unlock all locked VMAs in bulk. We also postpone unlocking the locked VMAs until the end of the update, when we do mmap_write_unlock. Potentially this keeps a VMA locked for longer than is absolutely necessary but it results in a big reduction of code complexity. Read-locking a VMA is done using two sequence numbers - one in the vm_area_struct and one in the mm_struct. VMA is considered read-locked when these sequence numbers are equal. To read-lock a VMA we set the sequence number in vm_area_struct to be equal to the sequence number in mm_struct. To unlock all VMAs we increment mm_struct's seq number. This allows for an efficient way to track locked VMAs and to drop the locks on all VMAs at the end of the update. The patchset implements per-VMA locking only for anonymous pages which are not in swap and avoids userfaultfs as their implementation is more complex. Additional support for file-back page faults, swapped and user pages can be added incrementally. Performance benchmarks show similar although slightly smaller benefits as with SPF patchset (~75% of SPF benefits). Still, with lower complexity this approach might be more desirable. Since RFC was posted in September 2022, two separate Google teams outside of Android evaluated the patchset and confirmed positive results. Here are the known usecases when per-VMA locks show benefits: Android: Apps with high number of threads (~100) launch times improve by up to 20%. Each thread mmaps several areas upon startup (Stack and Thread-local storage (TLS), thread signal stack, indirect ref table), which requires taking mmap_lock in write mode. Page faults take mmap_lock in read mode. During app launch, both thread creation and page faults establishing the active workinget are happening in parallel and that causes lock contention between mm writers and readers even if updates and page faults are happening in different VMAs. Per-vma locks prevent this contention by providing more granular lock. Google Fibers: We have several dynamically sized thread pools that spawn new threads under increased load and reduce their number when idling. For example, Google's in-process scheduling/threading framework, UMCG/Fibers, is backed by such a thread pool. When idling, only a small number of idle worker threads are available; when a spike of incoming requests arrive, each request is handled in its own "fiber", which is a work item posted onto a UMCG worker thread; quite often these spikes lead to a number of new threads spawning. Each new thread needs to allocate and register an RSEQ section on its TLS, then register itself with the kernel as a UMCG worker thread, and only after that it can be considered by the in-process UMCG/Fiber scheduler as available to do useful work. In short, during an incoming workload spike new threads have to be spawned, and they perform several syscalls (RSEQ registration, UMCG worker registration, memory allocations) before they can actually start doing useful work. Removing any bottlenecks on this thread startup path will greatly improve our services' latencies when faced with request/workload spikes. At high scale, mmap_lock contention during thread creation and stack page faults leads to user-visible multi-second serving latencies in a similar pattern to Android app startup. Per-VMA locking patchset has been run successfully in limited experiments with user-facing production workloads. In these experiments, we observed that the peak thread creation rate was high enough that thread creation is no longer a bottleneck. TCP zerocopy receive: From the point of view of TCP zerocopy receive, the per-vma lock patch is massively beneficial. In today's implementation, a process with N threads where N - 1 are performing zerocopy receive and 1 thread is performing madvise() with the write lock taken (e.g. needs to change vm_flags) will result in all N -1 receive threads blocking until the madvise is done. Conversely, on a busy process receiving a lot of data, an madvise operation that does need to take the mmap lock in write mode will need to wait for all of the receives to be done - a lose:lose proposition. Per-VMA locking _removes_ by definition this source of contention entirely. There are other benefits for receive as well, chiefly a reduction in cacheline bouncing across receiving threads for locking/unlocking the single mmap lock. On an RPC style synthetic workload with 4KB RPCs: 1a) The find+lock+unlock VMA path in the base case, without the per-vma lock patchset, is about 0.7% of cycles as measured by perf. 1b) mmap_read_lock + mmap_read_unlock in the base case is about 0.5% cycles overall - most of this is within the TCP read hotpath (a small fraction is 'other' usage in the system). 2a) The find+lock+unlock VMA path, with the per-vma patchset and a trivial patch written to take advantage of it in TCP, is about 0.4% of cycles (down from 0.7% above) 2b) mmap_read_lock + mmap_read_unlock in the per-vma patchset is < 0.1% cycles and is out of the TCP read hotpath entirely (down from 0.5% before, the remaining usage is the 'other' usage in the system). So, in addition to entirely removing an onerous source of contention, it also reduces the CPU cycles of TCP receive zerocopy by about 0.5%+ (compared to overall cycles in perf) for the 'small' RPC scenario. In https://lkml.kernel.org/r/87fsaqouyd.fsf_-_@stealth, Punit demonstrated throughput improvements of as much as 188% from this patchset. This patch (of 25): This configuration variable will be used to build the support for VMA locking during page fault handling. This is enabled on supported architectures with SMP and MMU set. The architecture support is needed since the page fault handler is called from the architecture's page faulting code which needs modifications to handle faults under VMA lock. Link: https://lkml.kernel.org/r/20230227173632.3292573-1-surenb@google.com Link: https://lkml.kernel.org/r/20230227173632.3292573-10-surenb@google.com Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1229 lines
38 KiB
Plaintext
1229 lines
38 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menu "Memory Management options"
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#
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# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
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# add proper SWAP support to them, in which case this can be remove.
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#
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config ARCH_NO_SWAP
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bool
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config ZPOOL
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bool
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menuconfig SWAP
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bool "Support for paging of anonymous memory (swap)"
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depends on MMU && BLOCK && !ARCH_NO_SWAP
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default y
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help
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This option allows you to choose whether you want to have support
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for so called swap devices or swap files in your kernel that are
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used to provide more virtual memory than the actual RAM present
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in your computer. If unsure say Y.
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config ZSWAP
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bool "Compressed cache for swap pages"
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depends on SWAP
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select FRONTSWAP
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select CRYPTO
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select ZPOOL
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help
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A lightweight compressed cache for swap pages. It takes
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pages that are in the process of being swapped out and attempts to
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compress them into a dynamically allocated RAM-based memory pool.
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This can result in a significant I/O reduction on swap device and,
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in the case where decompressing from RAM is faster than swap device
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reads, can also improve workload performance.
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config ZSWAP_DEFAULT_ON
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bool "Enable the compressed cache for swap pages by default"
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depends on ZSWAP
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help
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If selected, the compressed cache for swap pages will be enabled
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at boot, otherwise it will be disabled.
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The selection made here can be overridden by using the kernel
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command line 'zswap.enabled=' option.
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choice
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prompt "Default compressor"
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depends on ZSWAP
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default ZSWAP_COMPRESSOR_DEFAULT_LZO
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help
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Selects the default compression algorithm for the compressed cache
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for swap pages.
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For an overview what kind of performance can be expected from
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a particular compression algorithm please refer to the benchmarks
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available at the following LWN page:
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https://lwn.net/Articles/751795/
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If in doubt, select 'LZO'.
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The selection made here can be overridden by using the kernel
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command line 'zswap.compressor=' option.
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config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
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bool "Deflate"
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select CRYPTO_DEFLATE
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help
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Use the Deflate algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_LZO
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bool "LZO"
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select CRYPTO_LZO
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help
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Use the LZO algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_842
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bool "842"
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select CRYPTO_842
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help
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Use the 842 algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_LZ4
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bool "LZ4"
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select CRYPTO_LZ4
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help
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Use the LZ4 algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
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bool "LZ4HC"
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select CRYPTO_LZ4HC
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help
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Use the LZ4HC algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
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bool "zstd"
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select CRYPTO_ZSTD
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help
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Use the zstd algorithm as the default compression algorithm.
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endchoice
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config ZSWAP_COMPRESSOR_DEFAULT
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string
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depends on ZSWAP
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default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
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default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
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default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
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default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
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default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
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default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
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default ""
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choice
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prompt "Default allocator"
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depends on ZSWAP
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default ZSWAP_ZPOOL_DEFAULT_ZBUD
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help
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Selects the default allocator for the compressed cache for
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swap pages.
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The default is 'zbud' for compatibility, however please do
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read the description of each of the allocators below before
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making a right choice.
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The selection made here can be overridden by using the kernel
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command line 'zswap.zpool=' option.
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config ZSWAP_ZPOOL_DEFAULT_ZBUD
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bool "zbud"
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select ZBUD
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help
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Use the zbud allocator as the default allocator.
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config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
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bool "z3fold"
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select Z3FOLD
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help
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Use the z3fold allocator as the default allocator.
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config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
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bool "zsmalloc"
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select ZSMALLOC
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help
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Use the zsmalloc allocator as the default allocator.
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endchoice
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config ZSWAP_ZPOOL_DEFAULT
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string
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depends on ZSWAP
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default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
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default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
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default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
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default ""
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config ZBUD
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tristate "2:1 compression allocator (zbud)"
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depends on ZSWAP
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help
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A special purpose allocator for storing compressed pages.
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It is designed to store up to two compressed pages per physical
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page. While this design limits storage density, it has simple and
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deterministic reclaim properties that make it preferable to a higher
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density approach when reclaim will be used.
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config Z3FOLD
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tristate "3:1 compression allocator (z3fold)"
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depends on ZSWAP
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help
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A special purpose allocator for storing compressed pages.
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It is designed to store up to three compressed pages per physical
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page. It is a ZBUD derivative so the simplicity and determinism are
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still there.
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config ZSMALLOC
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tristate
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prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
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depends on MMU
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help
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zsmalloc is a slab-based memory allocator designed to store
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pages of various compression levels efficiently. It achieves
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the highest storage density with the least amount of fragmentation.
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config ZSMALLOC_STAT
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bool "Export zsmalloc statistics"
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depends on ZSMALLOC
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select DEBUG_FS
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help
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This option enables code in the zsmalloc to collect various
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statistics about what's happening in zsmalloc and exports that
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information to userspace via debugfs.
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If unsure, say N.
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config ZSMALLOC_CHAIN_SIZE
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int "Maximum number of physical pages per-zspage"
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default 8
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range 4 16
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depends on ZSMALLOC
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help
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This option sets the upper limit on the number of physical pages
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that a zmalloc page (zspage) can consist of. The optimal zspage
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chain size is calculated for each size class during the
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initialization of the pool.
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Changing this option can alter the characteristics of size classes,
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such as the number of pages per zspage and the number of objects
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per zspage. This can also result in different configurations of
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the pool, as zsmalloc merges size classes with similar
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characteristics.
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For more information, see zsmalloc documentation.
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menu "SLAB allocator options"
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choice
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prompt "Choose SLAB allocator"
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default SLUB
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help
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This option allows to select a slab allocator.
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config SLAB
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bool "SLAB"
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depends on !PREEMPT_RT
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select HAVE_HARDENED_USERCOPY_ALLOCATOR
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help
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The regular slab allocator that is established and known to work
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well in all environments. It organizes cache hot objects in
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per cpu and per node queues.
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config SLUB
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bool "SLUB (Unqueued Allocator)"
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select HAVE_HARDENED_USERCOPY_ALLOCATOR
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help
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SLUB is a slab allocator that minimizes cache line usage
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instead of managing queues of cached objects (SLAB approach).
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Per cpu caching is realized using slabs of objects instead
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of queues of objects. SLUB can use memory efficiently
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and has enhanced diagnostics. SLUB is the default choice for
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a slab allocator.
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config SLOB_DEPRECATED
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depends on EXPERT
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bool "SLOB (Simple Allocator - DEPRECATED)"
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depends on !PREEMPT_RT
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help
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Deprecated and scheduled for removal in a few cycles. SLUB
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recommended as replacement. CONFIG_SLUB_TINY can be considered
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on systems with 16MB or less RAM.
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If you need SLOB to stay, please contact linux-mm@kvack.org and
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people listed in the SLAB ALLOCATOR section of MAINTAINERS file,
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with your use case.
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SLOB replaces the stock allocator with a drastically simpler
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allocator. SLOB is generally more space efficient but
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does not perform as well on large systems.
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endchoice
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config SLOB
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bool
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default y
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depends on SLOB_DEPRECATED
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config SLUB_TINY
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bool "Configure SLUB for minimal memory footprint"
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depends on SLUB && EXPERT
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select SLAB_MERGE_DEFAULT
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help
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Configures the SLUB allocator in a way to achieve minimal memory
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footprint, sacrificing scalability, debugging and other features.
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This is intended only for the smallest system that had used the
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SLOB allocator and is not recommended for systems with more than
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16MB RAM.
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If unsure, say N.
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config SLAB_MERGE_DEFAULT
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bool "Allow slab caches to be merged"
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default y
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depends on SLAB || SLUB
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help
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For reduced kernel memory fragmentation, slab caches can be
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merged when they share the same size and other characteristics.
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This carries a risk of kernel heap overflows being able to
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overwrite objects from merged caches (and more easily control
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cache layout), which makes such heap attacks easier to exploit
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by attackers. By keeping caches unmerged, these kinds of exploits
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can usually only damage objects in the same cache. To disable
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merging at runtime, "slab_nomerge" can be passed on the kernel
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command line.
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config SLAB_FREELIST_RANDOM
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bool "Randomize slab freelist"
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depends on SLAB || (SLUB && !SLUB_TINY)
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help
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Randomizes the freelist order used on creating new pages. This
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security feature reduces the predictability of the kernel slab
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allocator against heap overflows.
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config SLAB_FREELIST_HARDENED
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bool "Harden slab freelist metadata"
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depends on SLAB || (SLUB && !SLUB_TINY)
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help
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Many kernel heap attacks try to target slab cache metadata and
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other infrastructure. This options makes minor performance
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sacrifices to harden the kernel slab allocator against common
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freelist exploit methods. Some slab implementations have more
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sanity-checking than others. This option is most effective with
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CONFIG_SLUB.
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config SLUB_STATS
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default n
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bool "Enable SLUB performance statistics"
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depends on SLUB && SYSFS && !SLUB_TINY
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help
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SLUB statistics are useful to debug SLUBs allocation behavior in
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order find ways to optimize the allocator. This should never be
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enabled for production use since keeping statistics slows down
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the allocator by a few percentage points. The slabinfo command
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supports the determination of the most active slabs to figure
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out which slabs are relevant to a particular load.
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Try running: slabinfo -DA
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config SLUB_CPU_PARTIAL
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default y
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depends on SLUB && SMP && !SLUB_TINY
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bool "SLUB per cpu partial cache"
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help
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Per cpu partial caches accelerate objects allocation and freeing
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that is local to a processor at the price of more indeterminism
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in the latency of the free. On overflow these caches will be cleared
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which requires the taking of locks that may cause latency spikes.
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Typically one would choose no for a realtime system.
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endmenu # SLAB allocator options
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config SHUFFLE_PAGE_ALLOCATOR
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bool "Page allocator randomization"
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default SLAB_FREELIST_RANDOM && ACPI_NUMA
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help
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Randomization of the page allocator improves the average
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utilization of a direct-mapped memory-side-cache. See section
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5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
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6.2a specification for an example of how a platform advertises
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the presence of a memory-side-cache. There are also incidental
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security benefits as it reduces the predictability of page
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allocations to compliment SLAB_FREELIST_RANDOM, but the
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default granularity of shuffling on the MAX_ORDER i.e, 10th
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order of pages is selected based on cache utilization benefits
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on x86.
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While the randomization improves cache utilization it may
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negatively impact workloads on platforms without a cache. For
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this reason, by default, the randomization is enabled only
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after runtime detection of a direct-mapped memory-side-cache.
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Otherwise, the randomization may be force enabled with the
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'page_alloc.shuffle' kernel command line parameter.
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Say Y if unsure.
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config COMPAT_BRK
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bool "Disable heap randomization"
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default y
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help
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Randomizing heap placement makes heap exploits harder, but it
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also breaks ancient binaries (including anything libc5 based).
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This option changes the bootup default to heap randomization
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disabled, and can be overridden at runtime by setting
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/proc/sys/kernel/randomize_va_space to 2.
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On non-ancient distros (post-2000 ones) N is usually a safe choice.
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config MMAP_ALLOW_UNINITIALIZED
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bool "Allow mmapped anonymous memory to be uninitialized"
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depends on EXPERT && !MMU
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default n
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help
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Normally, and according to the Linux spec, anonymous memory obtained
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from mmap() has its contents cleared before it is passed to
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userspace. Enabling this config option allows you to request that
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mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
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providing a huge performance boost. If this option is not enabled,
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then the flag will be ignored.
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This is taken advantage of by uClibc's malloc(), and also by
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ELF-FDPIC binfmt's brk and stack allocator.
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Because of the obvious security issues, this option should only be
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enabled on embedded devices where you control what is run in
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userspace. Since that isn't generally a problem on no-MMU systems,
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it is normally safe to say Y here.
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See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
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config SELECT_MEMORY_MODEL
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def_bool y
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depends on ARCH_SELECT_MEMORY_MODEL
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choice
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prompt "Memory model"
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depends on SELECT_MEMORY_MODEL
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default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
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default FLATMEM_MANUAL
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help
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This option allows you to change some of the ways that
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Linux manages its memory internally. Most users will
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only have one option here selected by the architecture
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configuration. This is normal.
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config FLATMEM_MANUAL
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bool "Flat Memory"
|
|
depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
|
|
help
|
|
This option is best suited for non-NUMA systems with
|
|
flat address space. The FLATMEM is the most efficient
|
|
system in terms of performance and resource consumption
|
|
and it is the best option for smaller systems.
|
|
|
|
For systems that have holes in their physical address
|
|
spaces and for features like NUMA and memory hotplug,
|
|
choose "Sparse Memory".
|
|
|
|
If unsure, choose this option (Flat Memory) over any other.
|
|
|
|
config SPARSEMEM_MANUAL
|
|
bool "Sparse Memory"
|
|
depends on ARCH_SPARSEMEM_ENABLE
|
|
help
|
|
This will be the only option for some systems, including
|
|
memory hot-plug systems. This is normal.
|
|
|
|
This option provides efficient support for systems with
|
|
holes is their physical address space and allows memory
|
|
hot-plug and hot-remove.
|
|
|
|
If unsure, choose "Flat Memory" over this option.
|
|
|
|
endchoice
|
|
|
|
config SPARSEMEM
|
|
def_bool y
|
|
depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
|
|
|
|
config FLATMEM
|
|
def_bool y
|
|
depends on !SPARSEMEM || FLATMEM_MANUAL
|
|
|
|
#
|
|
# SPARSEMEM_EXTREME (which is the default) does some bootmem
|
|
# allocations when sparse_init() is called. If this cannot
|
|
# be done on your architecture, select this option. However,
|
|
# statically allocating the mem_section[] array can potentially
|
|
# consume vast quantities of .bss, so be careful.
|
|
#
|
|
# This option will also potentially produce smaller runtime code
|
|
# with gcc 3.4 and later.
|
|
#
|
|
config SPARSEMEM_STATIC
|
|
bool
|
|
|
|
#
|
|
# Architecture platforms which require a two level mem_section in SPARSEMEM
|
|
# must select this option. This is usually for architecture platforms with
|
|
# an extremely sparse physical address space.
|
|
#
|
|
config SPARSEMEM_EXTREME
|
|
def_bool y
|
|
depends on SPARSEMEM && !SPARSEMEM_STATIC
|
|
|
|
config SPARSEMEM_VMEMMAP_ENABLE
|
|
bool
|
|
|
|
config SPARSEMEM_VMEMMAP
|
|
bool "Sparse Memory virtual memmap"
|
|
depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
|
|
default y
|
|
help
|
|
SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
|
|
pfn_to_page and page_to_pfn operations. This is the most
|
|
efficient option when sufficient kernel resources are available.
|
|
|
|
config HAVE_MEMBLOCK_PHYS_MAP
|
|
bool
|
|
|
|
config HAVE_FAST_GUP
|
|
depends on MMU
|
|
bool
|
|
|
|
# Don't discard allocated memory used to track "memory" and "reserved" memblocks
|
|
# after early boot, so it can still be used to test for validity of memory.
|
|
# Also, memblocks are updated with memory hot(un)plug.
|
|
config ARCH_KEEP_MEMBLOCK
|
|
bool
|
|
|
|
# Keep arch NUMA mapping infrastructure post-init.
|
|
config NUMA_KEEP_MEMINFO
|
|
bool
|
|
|
|
config MEMORY_ISOLATION
|
|
bool
|
|
|
|
# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
|
|
# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
|
|
# /dev/mem.
|
|
config EXCLUSIVE_SYSTEM_RAM
|
|
def_bool y
|
|
depends on !DEVMEM || STRICT_DEVMEM
|
|
|
|
#
|
|
# Only be set on architectures that have completely implemented memory hotplug
|
|
# feature. If you are not sure, don't touch it.
|
|
#
|
|
config HAVE_BOOTMEM_INFO_NODE
|
|
def_bool n
|
|
|
|
config ARCH_ENABLE_MEMORY_HOTPLUG
|
|
bool
|
|
|
|
config ARCH_ENABLE_MEMORY_HOTREMOVE
|
|
bool
|
|
|
|
# eventually, we can have this option just 'select SPARSEMEM'
|
|
menuconfig MEMORY_HOTPLUG
|
|
bool "Memory hotplug"
|
|
select MEMORY_ISOLATION
|
|
depends on SPARSEMEM
|
|
depends on ARCH_ENABLE_MEMORY_HOTPLUG
|
|
depends on 64BIT
|
|
select NUMA_KEEP_MEMINFO if NUMA
|
|
|
|
if MEMORY_HOTPLUG
|
|
|
|
config MEMORY_HOTPLUG_DEFAULT_ONLINE
|
|
bool "Online the newly added memory blocks by default"
|
|
depends on MEMORY_HOTPLUG
|
|
help
|
|
This option sets the default policy setting for memory hotplug
|
|
onlining policy (/sys/devices/system/memory/auto_online_blocks) which
|
|
determines what happens to newly added memory regions. Policy setting
|
|
can always be changed at runtime.
|
|
See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
|
|
|
|
Say Y here if you want all hot-plugged memory blocks to appear in
|
|
'online' state by default.
|
|
Say N here if you want the default policy to keep all hot-plugged
|
|
memory blocks in 'offline' state.
|
|
|
|
config MEMORY_HOTREMOVE
|
|
bool "Allow for memory hot remove"
|
|
select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
|
|
depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
|
|
depends on MIGRATION
|
|
|
|
config MHP_MEMMAP_ON_MEMORY
|
|
def_bool y
|
|
depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
|
|
depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
|
|
|
|
endif # MEMORY_HOTPLUG
|
|
|
|
# Heavily threaded applications may benefit from splitting the mm-wide
|
|
# page_table_lock, so that faults on different parts of the user address
|
|
# space can be handled with less contention: split it at this NR_CPUS.
|
|
# Default to 4 for wider testing, though 8 might be more appropriate.
|
|
# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
|
|
# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
|
|
# SPARC32 allocates multiple pte tables within a single page, and therefore
|
|
# a per-page lock leads to problems when multiple tables need to be locked
|
|
# at the same time (e.g. copy_page_range()).
|
|
# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
|
|
#
|
|
config SPLIT_PTLOCK_CPUS
|
|
int
|
|
default "999999" if !MMU
|
|
default "999999" if ARM && !CPU_CACHE_VIPT
|
|
default "999999" if PARISC && !PA20
|
|
default "999999" if SPARC32
|
|
default "4"
|
|
|
|
config ARCH_ENABLE_SPLIT_PMD_PTLOCK
|
|
bool
|
|
|
|
#
|
|
# support for memory balloon
|
|
config MEMORY_BALLOON
|
|
bool
|
|
|
|
#
|
|
# support for memory balloon compaction
|
|
config BALLOON_COMPACTION
|
|
bool "Allow for balloon memory compaction/migration"
|
|
def_bool y
|
|
depends on COMPACTION && MEMORY_BALLOON
|
|
help
|
|
Memory fragmentation introduced by ballooning might reduce
|
|
significantly the number of 2MB contiguous memory blocks that can be
|
|
used within a guest, thus imposing performance penalties associated
|
|
with the reduced number of transparent huge pages that could be used
|
|
by the guest workload. Allowing the compaction & migration for memory
|
|
pages enlisted as being part of memory balloon devices avoids the
|
|
scenario aforementioned and helps improving memory defragmentation.
|
|
|
|
#
|
|
# support for memory compaction
|
|
config COMPACTION
|
|
bool "Allow for memory compaction"
|
|
def_bool y
|
|
select MIGRATION
|
|
depends on MMU
|
|
help
|
|
Compaction is the only memory management component to form
|
|
high order (larger physically contiguous) memory blocks
|
|
reliably. The page allocator relies on compaction heavily and
|
|
the lack of the feature can lead to unexpected OOM killer
|
|
invocations for high order memory requests. You shouldn't
|
|
disable this option unless there really is a strong reason for
|
|
it and then we would be really interested to hear about that at
|
|
linux-mm@kvack.org.
|
|
|
|
config COMPACT_UNEVICTABLE_DEFAULT
|
|
int
|
|
depends on COMPACTION
|
|
default 0 if PREEMPT_RT
|
|
default 1
|
|
|
|
#
|
|
# support for free page reporting
|
|
config PAGE_REPORTING
|
|
bool "Free page reporting"
|
|
def_bool n
|
|
help
|
|
Free page reporting allows for the incremental acquisition of
|
|
free pages from the buddy allocator for the purpose of reporting
|
|
those pages to another entity, such as a hypervisor, so that the
|
|
memory can be freed within the host for other uses.
|
|
|
|
#
|
|
# support for page migration
|
|
#
|
|
config MIGRATION
|
|
bool "Page migration"
|
|
def_bool y
|
|
depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
|
|
help
|
|
Allows the migration of the physical location of pages of processes
|
|
while the virtual addresses are not changed. This is useful in
|
|
two situations. The first is on NUMA systems to put pages nearer
|
|
to the processors accessing. The second is when allocating huge
|
|
pages as migration can relocate pages to satisfy a huge page
|
|
allocation instead of reclaiming.
|
|
|
|
config DEVICE_MIGRATION
|
|
def_bool MIGRATION && ZONE_DEVICE
|
|
|
|
config ARCH_ENABLE_HUGEPAGE_MIGRATION
|
|
bool
|
|
|
|
config ARCH_ENABLE_THP_MIGRATION
|
|
bool
|
|
|
|
config HUGETLB_PAGE_SIZE_VARIABLE
|
|
def_bool n
|
|
help
|
|
Allows the pageblock_order value to be dynamic instead of just standard
|
|
HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
|
|
on a platform.
|
|
|
|
Note that the pageblock_order cannot exceed MAX_ORDER and will be
|
|
clamped down to MAX_ORDER.
|
|
|
|
config CONTIG_ALLOC
|
|
def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
|
|
|
|
config PHYS_ADDR_T_64BIT
|
|
def_bool 64BIT
|
|
|
|
config BOUNCE
|
|
bool "Enable bounce buffers"
|
|
default y
|
|
depends on BLOCK && MMU && HIGHMEM
|
|
help
|
|
Enable bounce buffers for devices that cannot access the full range of
|
|
memory available to the CPU. Enabled by default when HIGHMEM is
|
|
selected, but you may say n to override this.
|
|
|
|
config MMU_NOTIFIER
|
|
bool
|
|
select SRCU
|
|
select INTERVAL_TREE
|
|
|
|
config KSM
|
|
bool "Enable KSM for page merging"
|
|
depends on MMU
|
|
select XXHASH
|
|
help
|
|
Enable Kernel Samepage Merging: KSM periodically scans those areas
|
|
of an application's address space that an app has advised may be
|
|
mergeable. When it finds pages of identical content, it replaces
|
|
the many instances by a single page with that content, so
|
|
saving memory until one or another app needs to modify the content.
|
|
Recommended for use with KVM, or with other duplicative applications.
|
|
See Documentation/mm/ksm.rst for more information: KSM is inactive
|
|
until a program has madvised that an area is MADV_MERGEABLE, and
|
|
root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
|
|
|
|
config DEFAULT_MMAP_MIN_ADDR
|
|
int "Low address space to protect from user allocation"
|
|
depends on MMU
|
|
default 4096
|
|
help
|
|
This is the portion of low virtual memory which should be protected
|
|
from userspace allocation. Keeping a user from writing to low pages
|
|
can help reduce the impact of kernel NULL pointer bugs.
|
|
|
|
For most ia64, ppc64 and x86 users with lots of address space
|
|
a value of 65536 is reasonable and should cause no problems.
|
|
On arm and other archs it should not be higher than 32768.
|
|
Programs which use vm86 functionality or have some need to map
|
|
this low address space will need CAP_SYS_RAWIO or disable this
|
|
protection by setting the value to 0.
|
|
|
|
This value can be changed after boot using the
|
|
/proc/sys/vm/mmap_min_addr tunable.
|
|
|
|
config ARCH_SUPPORTS_MEMORY_FAILURE
|
|
bool
|
|
|
|
config MEMORY_FAILURE
|
|
depends on MMU
|
|
depends on ARCH_SUPPORTS_MEMORY_FAILURE
|
|
bool "Enable recovery from hardware memory errors"
|
|
select MEMORY_ISOLATION
|
|
select RAS
|
|
help
|
|
Enables code to recover from some memory failures on systems
|
|
with MCA recovery. This allows a system to continue running
|
|
even when some of its memory has uncorrected errors. This requires
|
|
special hardware support and typically ECC memory.
|
|
|
|
config HWPOISON_INJECT
|
|
tristate "HWPoison pages injector"
|
|
depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
|
|
select PROC_PAGE_MONITOR
|
|
|
|
config NOMMU_INITIAL_TRIM_EXCESS
|
|
int "Turn on mmap() excess space trimming before booting"
|
|
depends on !MMU
|
|
default 1
|
|
help
|
|
The NOMMU mmap() frequently needs to allocate large contiguous chunks
|
|
of memory on which to store mappings, but it can only ask the system
|
|
allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
|
|
more than it requires. To deal with this, mmap() is able to trim off
|
|
the excess and return it to the allocator.
|
|
|
|
If trimming is enabled, the excess is trimmed off and returned to the
|
|
system allocator, which can cause extra fragmentation, particularly
|
|
if there are a lot of transient processes.
|
|
|
|
If trimming is disabled, the excess is kept, but not used, which for
|
|
long-term mappings means that the space is wasted.
|
|
|
|
Trimming can be dynamically controlled through a sysctl option
|
|
(/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
|
|
excess pages there must be before trimming should occur, or zero if
|
|
no trimming is to occur.
|
|
|
|
This option specifies the initial value of this option. The default
|
|
of 1 says that all excess pages should be trimmed.
|
|
|
|
See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
|
|
|
|
config ARCH_WANT_GENERAL_HUGETLB
|
|
bool
|
|
|
|
config ARCH_WANTS_THP_SWAP
|
|
def_bool n
|
|
|
|
menuconfig TRANSPARENT_HUGEPAGE
|
|
bool "Transparent Hugepage Support"
|
|
depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
|
|
select COMPACTION
|
|
select XARRAY_MULTI
|
|
help
|
|
Transparent Hugepages allows the kernel to use huge pages and
|
|
huge tlb transparently to the applications whenever possible.
|
|
This feature can improve computing performance to certain
|
|
applications by speeding up page faults during memory
|
|
allocation, by reducing the number of tlb misses and by speeding
|
|
up the pagetable walking.
|
|
|
|
If memory constrained on embedded, you may want to say N.
|
|
|
|
if TRANSPARENT_HUGEPAGE
|
|
|
|
choice
|
|
prompt "Transparent Hugepage Support sysfs defaults"
|
|
depends on TRANSPARENT_HUGEPAGE
|
|
default TRANSPARENT_HUGEPAGE_ALWAYS
|
|
help
|
|
Selects the sysfs defaults for Transparent Hugepage Support.
|
|
|
|
config TRANSPARENT_HUGEPAGE_ALWAYS
|
|
bool "always"
|
|
help
|
|
Enabling Transparent Hugepage always, can increase the
|
|
memory footprint of applications without a guaranteed
|
|
benefit but it will work automatically for all applications.
|
|
|
|
config TRANSPARENT_HUGEPAGE_MADVISE
|
|
bool "madvise"
|
|
help
|
|
Enabling Transparent Hugepage madvise, will only provide a
|
|
performance improvement benefit to the applications using
|
|
madvise(MADV_HUGEPAGE) but it won't risk to increase the
|
|
memory footprint of applications without a guaranteed
|
|
benefit.
|
|
endchoice
|
|
|
|
config THP_SWAP
|
|
def_bool y
|
|
depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
|
|
help
|
|
Swap transparent huge pages in one piece, without splitting.
|
|
XXX: For now, swap cluster backing transparent huge page
|
|
will be split after swapout.
|
|
|
|
For selection by architectures with reasonable THP sizes.
|
|
|
|
config READ_ONLY_THP_FOR_FS
|
|
bool "Read-only THP for filesystems (EXPERIMENTAL)"
|
|
depends on TRANSPARENT_HUGEPAGE && SHMEM
|
|
|
|
help
|
|
Allow khugepaged to put read-only file-backed pages in THP.
|
|
|
|
This is marked experimental because it is a new feature. Write
|
|
support of file THPs will be developed in the next few release
|
|
cycles.
|
|
|
|
endif # TRANSPARENT_HUGEPAGE
|
|
|
|
#
|
|
# UP and nommu archs use km based percpu allocator
|
|
#
|
|
config NEED_PER_CPU_KM
|
|
depends on !SMP || !MMU
|
|
bool
|
|
default y
|
|
|
|
config NEED_PER_CPU_EMBED_FIRST_CHUNK
|
|
bool
|
|
|
|
config NEED_PER_CPU_PAGE_FIRST_CHUNK
|
|
bool
|
|
|
|
config USE_PERCPU_NUMA_NODE_ID
|
|
bool
|
|
|
|
config HAVE_SETUP_PER_CPU_AREA
|
|
bool
|
|
|
|
config FRONTSWAP
|
|
bool
|
|
|
|
config CMA
|
|
bool "Contiguous Memory Allocator"
|
|
depends on MMU
|
|
select MIGRATION
|
|
select MEMORY_ISOLATION
|
|
help
|
|
This enables the Contiguous Memory Allocator which allows other
|
|
subsystems to allocate big physically-contiguous blocks of memory.
|
|
CMA reserves a region of memory and allows only movable pages to
|
|
be allocated from it. This way, the kernel can use the memory for
|
|
pagecache and when a subsystem requests for contiguous area, the
|
|
allocated pages are migrated away to serve the contiguous request.
|
|
|
|
If unsure, say "n".
|
|
|
|
config CMA_DEBUG
|
|
bool "CMA debug messages (DEVELOPMENT)"
|
|
depends on DEBUG_KERNEL && CMA
|
|
help
|
|
Turns on debug messages in CMA. This produces KERN_DEBUG
|
|
messages for every CMA call as well as various messages while
|
|
processing calls such as dma_alloc_from_contiguous().
|
|
This option does not affect warning and error messages.
|
|
|
|
config CMA_DEBUGFS
|
|
bool "CMA debugfs interface"
|
|
depends on CMA && DEBUG_FS
|
|
help
|
|
Turns on the DebugFS interface for CMA.
|
|
|
|
config CMA_SYSFS
|
|
bool "CMA information through sysfs interface"
|
|
depends on CMA && SYSFS
|
|
help
|
|
This option exposes some sysfs attributes to get information
|
|
from CMA.
|
|
|
|
config CMA_AREAS
|
|
int "Maximum count of the CMA areas"
|
|
depends on CMA
|
|
default 19 if NUMA
|
|
default 7
|
|
help
|
|
CMA allows to create CMA areas for particular purpose, mainly,
|
|
used as device private area. This parameter sets the maximum
|
|
number of CMA area in the system.
|
|
|
|
If unsure, leave the default value "7" in UMA and "19" in NUMA.
|
|
|
|
config MEM_SOFT_DIRTY
|
|
bool "Track memory changes"
|
|
depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
|
|
select PROC_PAGE_MONITOR
|
|
help
|
|
This option enables memory changes tracking by introducing a
|
|
soft-dirty bit on pte-s. This bit it set when someone writes
|
|
into a page just as regular dirty bit, but unlike the latter
|
|
it can be cleared by hands.
|
|
|
|
See Documentation/admin-guide/mm/soft-dirty.rst for more details.
|
|
|
|
config GENERIC_EARLY_IOREMAP
|
|
bool
|
|
|
|
config STACK_MAX_DEFAULT_SIZE_MB
|
|
int "Default maximum user stack size for 32-bit processes (MB)"
|
|
default 100
|
|
range 8 2048
|
|
depends on STACK_GROWSUP && (!64BIT || COMPAT)
|
|
help
|
|
This is the maximum stack size in Megabytes in the VM layout of 32-bit
|
|
user processes when the stack grows upwards (currently only on parisc
|
|
arch) when the RLIMIT_STACK hard limit is unlimited.
|
|
|
|
A sane initial value is 100 MB.
|
|
|
|
config DEFERRED_STRUCT_PAGE_INIT
|
|
bool "Defer initialisation of struct pages to kthreads"
|
|
depends on SPARSEMEM
|
|
depends on !NEED_PER_CPU_KM
|
|
depends on 64BIT
|
|
select PADATA
|
|
help
|
|
Ordinarily all struct pages are initialised during early boot in a
|
|
single thread. On very large machines this can take a considerable
|
|
amount of time. If this option is set, large machines will bring up
|
|
a subset of memmap at boot and then initialise the rest in parallel.
|
|
This has a potential performance impact on tasks running early in the
|
|
lifetime of the system until these kthreads finish the
|
|
initialisation.
|
|
|
|
config PAGE_IDLE_FLAG
|
|
bool
|
|
select PAGE_EXTENSION if !64BIT
|
|
help
|
|
This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
|
|
bit writers can set the state of the bit in the flags so that PTE
|
|
Accessed bit readers may avoid disturbance.
|
|
|
|
config IDLE_PAGE_TRACKING
|
|
bool "Enable idle page tracking"
|
|
depends on SYSFS && MMU
|
|
select PAGE_IDLE_FLAG
|
|
help
|
|
This feature allows to estimate the amount of user pages that have
|
|
not been touched during a given period of time. This information can
|
|
be useful to tune memory cgroup limits and/or for job placement
|
|
within a compute cluster.
|
|
|
|
See Documentation/admin-guide/mm/idle_page_tracking.rst for
|
|
more details.
|
|
|
|
config ARCH_HAS_CACHE_LINE_SIZE
|
|
bool
|
|
|
|
config ARCH_HAS_CURRENT_STACK_POINTER
|
|
bool
|
|
help
|
|
In support of HARDENED_USERCOPY performing stack variable lifetime
|
|
checking, an architecture-agnostic way to find the stack pointer
|
|
is needed. Once an architecture defines an unsigned long global
|
|
register alias named "current_stack_pointer", this config can be
|
|
selected.
|
|
|
|
config ARCH_HAS_PTE_DEVMAP
|
|
bool
|
|
|
|
config ARCH_HAS_ZONE_DMA_SET
|
|
bool
|
|
|
|
config ZONE_DMA
|
|
bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
|
|
default y if ARM64 || X86
|
|
|
|
config ZONE_DMA32
|
|
bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
|
|
depends on !X86_32
|
|
default y if ARM64
|
|
|
|
config ZONE_DEVICE
|
|
bool "Device memory (pmem, HMM, etc...) hotplug support"
|
|
depends on MEMORY_HOTPLUG
|
|
depends on MEMORY_HOTREMOVE
|
|
depends on SPARSEMEM_VMEMMAP
|
|
depends on ARCH_HAS_PTE_DEVMAP
|
|
select XARRAY_MULTI
|
|
|
|
help
|
|
Device memory hotplug support allows for establishing pmem,
|
|
or other device driver discovered memory regions, in the
|
|
memmap. This allows pfn_to_page() lookups of otherwise
|
|
"device-physical" addresses which is needed for using a DAX
|
|
mapping in an O_DIRECT operation, among other things.
|
|
|
|
If FS_DAX is enabled, then say Y.
|
|
|
|
#
|
|
# Helpers to mirror range of the CPU page tables of a process into device page
|
|
# tables.
|
|
#
|
|
config HMM_MIRROR
|
|
bool
|
|
depends on MMU
|
|
|
|
config GET_FREE_REGION
|
|
depends on SPARSEMEM
|
|
bool
|
|
|
|
config DEVICE_PRIVATE
|
|
bool "Unaddressable device memory (GPU memory, ...)"
|
|
depends on ZONE_DEVICE
|
|
select GET_FREE_REGION
|
|
|
|
help
|
|
Allows creation of struct pages to represent unaddressable device
|
|
memory; i.e., memory that is only accessible from the device (or
|
|
group of devices). You likely also want to select HMM_MIRROR.
|
|
|
|
config VMAP_PFN
|
|
bool
|
|
|
|
config ARCH_USES_HIGH_VMA_FLAGS
|
|
bool
|
|
config ARCH_HAS_PKEYS
|
|
bool
|
|
|
|
config ARCH_USES_PG_ARCH_X
|
|
bool
|
|
help
|
|
Enable the definition of PG_arch_x page flags with x > 1. Only
|
|
suitable for 64-bit architectures with CONFIG_FLATMEM or
|
|
CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
|
|
enough room for additional bits in page->flags.
|
|
|
|
config VM_EVENT_COUNTERS
|
|
default y
|
|
bool "Enable VM event counters for /proc/vmstat" if EXPERT
|
|
help
|
|
VM event counters are needed for event counts to be shown.
|
|
This option allows the disabling of the VM event counters
|
|
on EXPERT systems. /proc/vmstat will only show page counts
|
|
if VM event counters are disabled.
|
|
|
|
config PERCPU_STATS
|
|
bool "Collect percpu memory statistics"
|
|
help
|
|
This feature collects and exposes statistics via debugfs. The
|
|
information includes global and per chunk statistics, which can
|
|
be used to help understand percpu memory usage.
|
|
|
|
config GUP_TEST
|
|
bool "Enable infrastructure for get_user_pages()-related unit tests"
|
|
depends on DEBUG_FS
|
|
help
|
|
Provides /sys/kernel/debug/gup_test, which in turn provides a way
|
|
to make ioctl calls that can launch kernel-based unit tests for
|
|
the get_user_pages*() and pin_user_pages*() family of API calls.
|
|
|
|
These tests include benchmark testing of the _fast variants of
|
|
get_user_pages*() and pin_user_pages*(), as well as smoke tests of
|
|
the non-_fast variants.
|
|
|
|
There is also a sub-test that allows running dump_page() on any
|
|
of up to eight pages (selected by command line args) within the
|
|
range of user-space addresses. These pages are either pinned via
|
|
pin_user_pages*(), or pinned via get_user_pages*(), as specified
|
|
by other command line arguments.
|
|
|
|
See tools/testing/selftests/mm/gup_test.c
|
|
|
|
comment "GUP_TEST needs to have DEBUG_FS enabled"
|
|
depends on !GUP_TEST && !DEBUG_FS
|
|
|
|
config GUP_GET_PXX_LOW_HIGH
|
|
bool
|
|
|
|
config DMAPOOL_TEST
|
|
tristate "Enable a module to run time tests on dma_pool"
|
|
depends on HAS_DMA
|
|
help
|
|
Provides a test module that will allocate and free many blocks of
|
|
various sizes and report how long it takes. This is intended to
|
|
provide a consistent way to measure how changes to the
|
|
dma_pool_alloc/free routines affect performance.
|
|
|
|
config ARCH_HAS_PTE_SPECIAL
|
|
bool
|
|
|
|
#
|
|
# Some architectures require a special hugepage directory format that is
|
|
# required to support multiple hugepage sizes. For example a4fe3ce76
|
|
# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
|
|
# introduced it on powerpc. This allows for a more flexible hugepage
|
|
# pagetable layouts.
|
|
#
|
|
config ARCH_HAS_HUGEPD
|
|
bool
|
|
|
|
config MAPPING_DIRTY_HELPERS
|
|
bool
|
|
|
|
config KMAP_LOCAL
|
|
bool
|
|
|
|
config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
|
|
bool
|
|
|
|
# struct io_mapping based helper. Selected by drivers that need them
|
|
config IO_MAPPING
|
|
bool
|
|
|
|
config SECRETMEM
|
|
default y
|
|
bool "Enable memfd_secret() system call" if EXPERT
|
|
depends on ARCH_HAS_SET_DIRECT_MAP
|
|
help
|
|
Enable the memfd_secret() system call with the ability to create
|
|
memory areas visible only in the context of the owning process and
|
|
not mapped to other processes and other kernel page tables.
|
|
|
|
config ANON_VMA_NAME
|
|
bool "Anonymous VMA name support"
|
|
depends on PROC_FS && ADVISE_SYSCALLS && MMU
|
|
|
|
help
|
|
Allow naming anonymous virtual memory areas.
|
|
|
|
This feature allows assigning names to virtual memory areas. Assigned
|
|
names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
|
|
and help identifying individual anonymous memory areas.
|
|
Assigning a name to anonymous virtual memory area might prevent that
|
|
area from being merged with adjacent virtual memory areas due to the
|
|
difference in their name.
|
|
|
|
config USERFAULTFD
|
|
bool "Enable userfaultfd() system call"
|
|
depends on MMU
|
|
help
|
|
Enable the userfaultfd() system call that allows to intercept and
|
|
handle page faults in userland.
|
|
|
|
config HAVE_ARCH_USERFAULTFD_WP
|
|
bool
|
|
help
|
|
Arch has userfaultfd write protection support
|
|
|
|
config HAVE_ARCH_USERFAULTFD_MINOR
|
|
bool
|
|
help
|
|
Arch has userfaultfd minor fault support
|
|
|
|
config PTE_MARKER_UFFD_WP
|
|
bool "Userfaultfd write protection support for shmem/hugetlbfs"
|
|
default y
|
|
depends on HAVE_ARCH_USERFAULTFD_WP
|
|
|
|
help
|
|
Allows to create marker PTEs for userfaultfd write protection
|
|
purposes. It is required to enable userfaultfd write protection on
|
|
file-backed memory types like shmem and hugetlbfs.
|
|
|
|
# multi-gen LRU {
|
|
config LRU_GEN
|
|
bool "Multi-Gen LRU"
|
|
depends on MMU
|
|
# make sure folio->flags has enough spare bits
|
|
depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
|
|
help
|
|
A high performance LRU implementation to overcommit memory. See
|
|
Documentation/admin-guide/mm/multigen_lru.rst for details.
|
|
|
|
config LRU_GEN_ENABLED
|
|
bool "Enable by default"
|
|
depends on LRU_GEN
|
|
help
|
|
This option enables the multi-gen LRU by default.
|
|
|
|
config LRU_GEN_STATS
|
|
bool "Full stats for debugging"
|
|
depends on LRU_GEN
|
|
help
|
|
Do not enable this option unless you plan to look at historical stats
|
|
from evicted generations for debugging purpose.
|
|
|
|
This option has a per-memcg and per-node memory overhead.
|
|
# }
|
|
|
|
config ARCH_SUPPORTS_PER_VMA_LOCK
|
|
def_bool n
|
|
|
|
config PER_VMA_LOCK
|
|
def_bool y
|
|
depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
|
|
help
|
|
Allow per-vma locking during page fault handling.
|
|
|
|
This feature allows locking each virtual memory area separately when
|
|
handling page faults instead of taking mmap_lock.
|
|
|
|
source "mm/damon/Kconfig"
|
|
|
|
endmenu
|