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Yu Zhao 95599ef684 mm/codetag: fix pgalloc_tag_split() 
The current assumption is that a large folio can only be split into
order-0 folios.  That is not the case for hugeTLB demotion, nor for THP
split: see commit c010d47f10 ("mm: thp: split huge page to any lower
order pages").

When a large folio is split into ones of a lower non-zero order, only the
new head pages should be tagged.  Tagging tail pages can cause imbalanced
"calls" counters, since only head pages are untagged by pgalloc_tag_sub()
and the "calls" counts on tail pages are leaked, e.g.,

  # echo 2048kB >/sys/kernel/mm/hugepages/hugepages-1048576kB/demote_size
  # echo 700 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
  # time echo 700 >/sys/kernel/mm/hugepages/hugepages-1048576kB/demote
  # echo 0 >/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
  # grep alloc_gigantic_folio /proc/allocinfo

Before this patch:
  0  549427200  mm/hugetlb.c:1549 func:alloc_gigantic_folio

  real  0m2.057s
  user  0m0.000s
  sys   0m2.051s

After this patch:
  0          0  mm/hugetlb.c:1549 func:alloc_gigantic_folio

  real  0m1.711s
  user  0m0.000s
  sys   0m1.704s

Not tagging tail pages also improves the splitting time, e.g., by about
15% when demoting 1GB hugeTLB folios to 2MB ones, as shown above.

Link: https://lkml.kernel.org/r/20240906042108.1150526-2-yuzhao@google.com
Fixes: be25d1d4e8 ("mm: create new codetag references during page splitting")
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-09-09 16:39:18 -07:00
arch mm: pass vm_flags to generic_get_unmapped_area() 2024-09-09 16:39:13 -07:00
block block: fix detection of unsupported WRITE SAME in blkdev_issue_write_zeroes 2024-08-28 08:49:25 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation zram: support priority parameter in recompression 2024-09-09 16:39:12 -07:00
drivers zram: support priority parameter in recompression 2024-09-09 16:39:12 -07:00
fs mm,tmpfs: consider end of file write in shmem_is_huge 2024-09-09 16:39:12 -07:00
include mm/codetag: fix pgalloc_tag_split() 2024-09-09 16:39:18 -07:00
init mm: fix typo in Kconfig 2024-09-01 20:25:45 -07:00
io_uring io_uring/kbuf: return correct iovec count from classic buffer peek 2024-08-30 10:45:54 -06:00
ipc ipc/shm, mm: drop do_vma_munmap() 2024-09-03 21:15:52 -07:00
kernel cgroup: clarify css sibling linkage is protected by cgroup_mutex or RCU 2024-09-09 16:39:15 -07:00
lib maple_tree: mark three functions as __maybe_unused 2024-09-09 16:39:17 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/codetag: fix pgalloc_tag_split() 2024-09-09 16:39:18 -07:00
net Including fixes from bluetooth, wireless and netfilter. 2024-08-30 06:14:39 +12:00
rust Rust fixes for v6.11 2024-08-16 11:24:06 -07:00
samples kmemleak-test: add percpu leak 2024-09-01 20:25:50 -07:00
scripts kasan: simplify and clarify Makefile 2024-09-03 21:15:35 -07:00
security Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging 2024-09-01 09:18:48 +12:00
sound sound fixes for 6.11-rc6 2024-08-28 06:24:22 +12:00
tools selftests/mm: relax test to fail after 100 migration failures 2024-09-09 16:39:05 -07:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX) 2024-08-14 12:28:24 -04:00
.clang-format Docs: Move clang-format from process/ to dev-tools/ 2024-06-26 16:36:00 -06:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: add script and target to generate pacman package 2024-07-22 01:24:22 +09:00
.mailmap ARM: SoC fixes for 6.11, part 2 2024-09-01 06:42:13 +12:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS tracing: Update of MAINTAINERS and CREDITS file 2024-07-18 14:08:42 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS tools: add skeleton code for userland testing of VMA logic 2024-09-01 20:25:55 -07:00
Makefile Linux 6.11-rc6 2024-09-01 19:46:02 +12:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

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 reStructuredText 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.