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The soft-dirty is a bit on a PTE which helps to track which pages a task
writes to. In order to do this tracking one should
1. Clear soft-dirty bits from PTEs ("echo 4 > /proc/PID/clear_refs)
2. Wait some time.
3. Read soft-dirty bits (55'th in /proc/PID/pagemap2 entries)
To do this tracking, the writable bit is cleared from PTEs when the
soft-dirty bit is. Thus, after this, when the task tries to modify a
page at some virtual address the #PF occurs and the kernel sets the
soft-dirty bit on the respective PTE.
Note, that although all the task's address space is marked as r/o after
the soft-dirty bits clear, the #PF-s that occur after that are processed
fast. This is so, since the pages are still mapped to physical memory,
and thus all the kernel does is finds this fact out and puts back
writable, dirty and soft-dirty bits on the PTE.
Another thing to note, is that when mremap moves PTEs they are marked
with soft-dirty as well, since from the user perspective mremap modifies
the virtual memory at mremap's new address.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
437 lines
12 KiB
Plaintext
437 lines
12 KiB
Plaintext
#
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# General architecture dependent options
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#
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config OPROFILE
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tristate "OProfile system profiling"
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depends on PROFILING
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depends on HAVE_OPROFILE
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select RING_BUFFER
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select RING_BUFFER_ALLOW_SWAP
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help
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OProfile is a profiling system capable of profiling the
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whole system, include the kernel, kernel modules, libraries,
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and applications.
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If unsure, say N.
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config OPROFILE_EVENT_MULTIPLEX
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bool "OProfile multiplexing support (EXPERIMENTAL)"
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default n
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depends on OPROFILE && X86
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help
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The number of hardware counters is limited. The multiplexing
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feature enables OProfile to gather more events than counters
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are provided by the hardware. This is realized by switching
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between events at an user specified time interval.
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If unsure, say N.
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config HAVE_OPROFILE
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bool
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config OPROFILE_NMI_TIMER
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def_bool y
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depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
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config KPROBES
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bool "Kprobes"
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depends on MODULES
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depends on HAVE_KPROBES
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select KALLSYMS
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help
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Kprobes allows you to trap at almost any kernel address and
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execute a callback function. register_kprobe() establishes
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a probepoint and specifies the callback. Kprobes is useful
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for kernel debugging, non-intrusive instrumentation and testing.
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If in doubt, say "N".
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config JUMP_LABEL
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bool "Optimize very unlikely/likely branches"
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depends on HAVE_ARCH_JUMP_LABEL
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help
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This option enables a transparent branch optimization that
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makes certain almost-always-true or almost-always-false branch
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conditions even cheaper to execute within the kernel.
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Certain performance-sensitive kernel code, such as trace points,
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scheduler functionality, networking code and KVM have such
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branches and include support for this optimization technique.
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If it is detected that the compiler has support for "asm goto",
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the kernel will compile such branches with just a nop
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instruction. When the condition flag is toggled to true, the
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nop will be converted to a jump instruction to execute the
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conditional block of instructions.
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This technique lowers overhead and stress on the branch prediction
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of the processor and generally makes the kernel faster. The update
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of the condition is slower, but those are always very rare.
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( On 32-bit x86, the necessary options added to the compiler
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flags may increase the size of the kernel slightly. )
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config OPTPROBES
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def_bool y
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depends on KPROBES && HAVE_OPTPROBES
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depends on !PREEMPT
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config KPROBES_ON_FTRACE
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def_bool y
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depends on KPROBES && HAVE_KPROBES_ON_FTRACE
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depends on DYNAMIC_FTRACE_WITH_REGS
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help
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If function tracer is enabled and the arch supports full
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passing of pt_regs to function tracing, then kprobes can
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optimize on top of function tracing.
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config UPROBES
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bool "Transparent user-space probes (EXPERIMENTAL)"
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depends on UPROBE_EVENT && PERF_EVENTS
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default n
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select PERCPU_RWSEM
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help
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Uprobes is the user-space counterpart to kprobes: they
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enable instrumentation applications (such as 'perf probe')
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to establish unintrusive probes in user-space binaries and
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libraries, by executing handler functions when the probes
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are hit by user-space applications.
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( These probes come in the form of single-byte breakpoints,
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managed by the kernel and kept transparent to the probed
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application. )
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If in doubt, say "N".
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config HAVE_64BIT_ALIGNED_ACCESS
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def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
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help
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Some architectures require 64 bit accesses to be 64 bit
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aligned, which also requires structs containing 64 bit values
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to be 64 bit aligned too. This includes some 32 bit
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architectures which can do 64 bit accesses, as well as 64 bit
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architectures without unaligned access.
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This symbol should be selected by an architecture if 64 bit
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accesses are required to be 64 bit aligned in this way even
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though it is not a 64 bit architecture.
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See Documentation/unaligned-memory-access.txt for more
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information on the topic of unaligned memory accesses.
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config HAVE_EFFICIENT_UNALIGNED_ACCESS
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bool
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help
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Some architectures are unable to perform unaligned accesses
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without the use of get_unaligned/put_unaligned. Others are
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unable to perform such accesses efficiently (e.g. trap on
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unaligned access and require fixing it up in the exception
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handler.)
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This symbol should be selected by an architecture if it can
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perform unaligned accesses efficiently to allow different
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code paths to be selected for these cases. Some network
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drivers, for example, could opt to not fix up alignment
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problems with received packets if doing so would not help
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much.
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See Documentation/unaligned-memory-access.txt for more
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information on the topic of unaligned memory accesses.
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config ARCH_USE_BUILTIN_BSWAP
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bool
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help
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Modern versions of GCC (since 4.4) have builtin functions
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for handling byte-swapping. Using these, instead of the old
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inline assembler that the architecture code provides in the
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__arch_bswapXX() macros, allows the compiler to see what's
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happening and offers more opportunity for optimisation. In
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particular, the compiler will be able to combine the byteswap
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with a nearby load or store and use load-and-swap or
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store-and-swap instructions if the architecture has them. It
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should almost *never* result in code which is worse than the
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hand-coded assembler in <asm/swab.h>. But just in case it
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does, the use of the builtins is optional.
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Any architecture with load-and-swap or store-and-swap
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instructions should set this. And it shouldn't hurt to set it
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on architectures that don't have such instructions.
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config KRETPROBES
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def_bool y
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depends on KPROBES && HAVE_KRETPROBES
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config USER_RETURN_NOTIFIER
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bool
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depends on HAVE_USER_RETURN_NOTIFIER
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help
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Provide a kernel-internal notification when a cpu is about to
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switch to user mode.
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config HAVE_IOREMAP_PROT
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bool
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config HAVE_KPROBES
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bool
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config HAVE_KRETPROBES
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bool
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config HAVE_OPTPROBES
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bool
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config HAVE_KPROBES_ON_FTRACE
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bool
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config HAVE_NMI_WATCHDOG
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bool
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#
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# An arch should select this if it provides all these things:
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#
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# task_pt_regs() in asm/processor.h or asm/ptrace.h
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# arch_has_single_step() if there is hardware single-step support
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# arch_has_block_step() if there is hardware block-step support
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# asm/syscall.h supplying asm-generic/syscall.h interface
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# linux/regset.h user_regset interfaces
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# CORE_DUMP_USE_REGSET #define'd in linux/elf.h
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# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit}
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# TIF_NOTIFY_RESUME calls tracehook_notify_resume()
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# signal delivery calls tracehook_signal_handler()
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#
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config HAVE_ARCH_TRACEHOOK
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bool
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config HAVE_DMA_ATTRS
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bool
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config HAVE_DMA_CONTIGUOUS
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bool
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config USE_GENERIC_SMP_HELPERS
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bool
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config GENERIC_SMP_IDLE_THREAD
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bool
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config GENERIC_IDLE_POLL_SETUP
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bool
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# Select if arch init_task initializer is different to init/init_task.c
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config ARCH_INIT_TASK
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bool
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# Select if arch has its private alloc_task_struct() function
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config ARCH_TASK_STRUCT_ALLOCATOR
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bool
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# Select if arch has its private alloc_thread_info() function
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config ARCH_THREAD_INFO_ALLOCATOR
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bool
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config HAVE_REGS_AND_STACK_ACCESS_API
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bool
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help
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This symbol should be selected by an architecure if it supports
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the API needed to access registers and stack entries from pt_regs,
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declared in asm/ptrace.h
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For example the kprobes-based event tracer needs this API.
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config HAVE_CLK
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bool
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help
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The <linux/clk.h> calls support software clock gating and
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thus are a key power management tool on many systems.
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config HAVE_DMA_API_DEBUG
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bool
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config HAVE_HW_BREAKPOINT
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bool
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depends on PERF_EVENTS
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config HAVE_MIXED_BREAKPOINTS_REGS
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bool
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depends on HAVE_HW_BREAKPOINT
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help
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Depending on the arch implementation of hardware breakpoints,
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some of them have separate registers for data and instruction
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breakpoints addresses, others have mixed registers to store
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them but define the access type in a control register.
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Select this option if your arch implements breakpoints under the
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latter fashion.
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config HAVE_USER_RETURN_NOTIFIER
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bool
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config HAVE_PERF_EVENTS_NMI
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bool
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help
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System hardware can generate an NMI using the perf event
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subsystem. Also has support for calculating CPU cycle events
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to determine how many clock cycles in a given period.
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config HAVE_PERF_REGS
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bool
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help
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Support selective register dumps for perf events. This includes
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bit-mapping of each registers and a unique architecture id.
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config HAVE_PERF_USER_STACK_DUMP
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bool
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help
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Support user stack dumps for perf event samples. This needs
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access to the user stack pointer which is not unified across
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architectures.
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config HAVE_ARCH_JUMP_LABEL
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bool
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config HAVE_ARCH_MUTEX_CPU_RELAX
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bool
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config HAVE_RCU_TABLE_FREE
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bool
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config ARCH_HAVE_NMI_SAFE_CMPXCHG
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bool
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config HAVE_ALIGNED_STRUCT_PAGE
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bool
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help
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This makes sure that struct pages are double word aligned and that
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e.g. the SLUB allocator can perform double word atomic operations
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on a struct page for better performance. However selecting this
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might increase the size of a struct page by a word.
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config HAVE_CMPXCHG_LOCAL
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bool
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config HAVE_CMPXCHG_DOUBLE
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bool
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config ARCH_WANT_IPC_PARSE_VERSION
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bool
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config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
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bool
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config ARCH_WANT_OLD_COMPAT_IPC
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select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
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bool
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config HAVE_ARCH_SECCOMP_FILTER
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bool
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help
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An arch should select this symbol if it provides all of these things:
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- syscall_get_arch()
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- syscall_get_arguments()
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- syscall_rollback()
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- syscall_set_return_value()
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- SIGSYS siginfo_t support
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- secure_computing is called from a ptrace_event()-safe context
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- secure_computing return value is checked and a return value of -1
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results in the system call being skipped immediately.
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config SECCOMP_FILTER
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def_bool y
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depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
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help
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Enable tasks to build secure computing environments defined
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in terms of Berkeley Packet Filter programs which implement
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task-defined system call filtering polices.
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See Documentation/prctl/seccomp_filter.txt for details.
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config HAVE_CONTEXT_TRACKING
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bool
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help
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Provide kernel/user boundaries probes necessary for subsystems
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that need it, such as userspace RCU extended quiescent state.
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Syscalls need to be wrapped inside user_exit()-user_enter() through
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the slow path using TIF_NOHZ flag. Exceptions handlers must be
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wrapped as well. Irqs are already protected inside
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rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
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irq exit still need to be protected.
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config HAVE_VIRT_CPU_ACCOUNTING
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bool
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config HAVE_IRQ_TIME_ACCOUNTING
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bool
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help
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Archs need to ensure they use a high enough resolution clock to
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support irq time accounting and then call enable_sched_clock_irqtime().
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config HAVE_ARCH_TRANSPARENT_HUGEPAGE
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bool
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config HAVE_ARCH_SOFT_DIRTY
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bool
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config HAVE_MOD_ARCH_SPECIFIC
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bool
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help
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The arch uses struct mod_arch_specific to store data. Many arches
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just need a simple module loader without arch specific data - those
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should not enable this.
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config MODULES_USE_ELF_RELA
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bool
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help
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Modules only use ELF RELA relocations. Modules with ELF REL
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relocations will give an error.
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config MODULES_USE_ELF_REL
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bool
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help
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Modules only use ELF REL relocations. Modules with ELF RELA
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relocations will give an error.
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config HAVE_UNDERSCORE_SYMBOL_PREFIX
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bool
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help
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Some architectures generate an _ in front of C symbols; things like
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module loading and assembly files need to know about this.
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#
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# ABI hall of shame
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#
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config CLONE_BACKWARDS
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bool
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help
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Architecture has tls passed as the 4th argument of clone(2),
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not the 5th one.
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config CLONE_BACKWARDS2
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bool
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help
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Architecture has the first two arguments of clone(2) swapped.
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config ODD_RT_SIGACTION
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bool
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help
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Architecture has unusual rt_sigaction(2) arguments
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config OLD_SIGSUSPEND
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bool
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help
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Architecture has old sigsuspend(2) syscall, of one-argument variety
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config OLD_SIGSUSPEND3
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bool
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help
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Even weirder antique ABI - three-argument sigsuspend(2)
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config OLD_SIGACTION
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bool
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help
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Architecture has old sigaction(2) syscall. Nope, not the same
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as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
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but fairly different variant of sigaction(2), thanks to OSF/1
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compatibility...
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config COMPAT_OLD_SIGACTION
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bool
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source "kernel/gcov/Kconfig"
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