df2ff39e78
Currently cma areas without a fixed base are allocated close to the end of the node. This placement is sub-optimal because of compaction: it brings pages into the cma area. In particular, it can bring in hot executable pages, even if there is a plenty of free memory on the machine. This results in cma allocation failures. Instead let's place cma areas close to the beginning of a node. In this case the compaction will help to free cma areas, resulting in better cma allocation success rates. If there is enough memory let's try to allocate bottom-up starting with 4GB to exclude any possible interference with DMA32. On smaller machines or in a case of a failure, stick with the old behavior. 16GB vm, 2GB cma area: With this patch: [ 0.000000] Command line: root=/dev/vda3 rootflags=subvol=/root systemd.unified_cgroup_hierarchy=1 enforcing=0 console=ttyS0,115200 hugetlb_cma=2G [ 0.002928] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node [ 0.002930] cma: Reserved 2048 MiB at 0x0000000100000000 [ 0.002931] hugetlb_cma: reserved 2048 MiB on node 0 Without this patch: [ 0.000000] Command line: root=/dev/vda3 rootflags=subvol=/root systemd.unified_cgroup_hierarchy=1 enforcing=0 console=ttyS0,115200 hugetlb_cma=2G [ 0.002930] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node [ 0.002933] cma: Reserved 2048 MiB at 0x00000003c0000000 [ 0.002934] hugetlb_cma: reserved 2048 MiB on node 0 v2: - switched to memblock_set_bottom_up(true), by Mike - start with 4GB, by Mike [guro@fb.com: whitespace fix, per Mike] Link: https://lkml.kernel.org/r/20201221170551.GB3428478@carbon.DHCP.thefacebook.com [guro@fb.com: fix 32-bit warnings] Link: https://lkml.kernel.org/r/20201223163537.GA4011967@carbon.DHCP.thefacebook.com [guro@fb.com: fix 32-bit systems] [akpm@linux-foundation.org: build fix] Link: https://lkml.kernel.org/r/20201217201214.3414100-1-guro@fb.com Signed-off-by: Roman Gushchin <guro@fb.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Cc: Wonhyuk Yang <vvghjk1234@gmail.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Rik van Riel <riel@surriel.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.