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Joao Martins 0fa5bc4023 mm/hugetlb: grab head page refcount once for group of subpages 
Patch series "mm/hugetlb: follow_hugetlb_page() improvements", v2.

While looking at ZONE_DEVICE struct page reuse particularly the last
patch[0], I found two possible improvements for follow_hugetlb_page()
which is solely used for get_user_pages()/pin_user_pages().

The first patch batches page refcount updates while the second tidies up
storing the subpages/vmas.  Both together bring the cost of slow variant
of gup() cost from ~87.6k usecs to ~5.8k usecs.

libhugetlbfs tests seem to pass as well gup_test benchmarks with hugetlbfs
vmas.

This patch (of 2):

follow_hugetlb_page() once it locks the pmd/pud, checks all its N subpages
in a huge page and grabs a reference for each one.  Similar to gup-fast,
have follow_hugetlb_page() grab the head page refcount only after counting
all its subpages that are part of the just faulted huge page.

Consequently we reduce the number of atomics necessary to pin said huge
page, which improves non-fast gup() considerably:

  - 16G with 1G huge page size
  gup_test -f /mnt/huge/file -m 16384 -r 10 -L -S -n 512 -w

PIN_LONGTERM_BENCHMARK: ~87.6k us -> ~12.8k us

Link: https://lkml.kernel.org/r/20210128182632.24562-1-joao.m.martins@oracle.com
Link: https://lkml.kernel.org/r/20210128182632.24562-2-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-02-24 13:38:32 -08:00
arch MIPS: do not call flush_tlb_all when setting pmd entry 2021-02-24 13:38:32 -08:00
block for-5.12/block-ipi-2021-02-21 2021-02-22 10:53:05 -08:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto Keyrings miscellany 2021-02-23 16:09:23 -08:00
Documentation mm/gfp: add kernel-doc for gfp_t 2021-02-24 13:38:32 -08:00
drivers video: fbdev: acornfb: remove free_unused_pages() 2021-02-24 13:38:31 -08:00
fs vmalloc: remove redundant NULL check 2021-02-24 13:38:30 -08:00
include mm/hugetlb: grab head page refcount once for group of subpages 2021-02-24 13:38:32 -08:00
init mm, slub: remove slub_memcg_sysfs boot param and CONFIG_SLUB_MEMCG_SYSFS_ON 2021-02-24 13:38:27 -08:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel Keyrings miscellany 2021-02-23 16:09:23 -08:00
lib kasan: don't run tests when KASAN is not enabled 2021-02-24 13:38:31 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm/hugetlb: grab head page refcount once for group of subpages 2021-02-24 13:38:32 -08:00
net idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
samples Keyrings miscellany 2021-02-23 16:09:23 -08:00
scripts scripts/spelling.txt: add more spellings to spelling.txt 2021-02-24 13:38:26 -08:00
security Keyrings miscellany 2021-02-23 16:09:23 -08:00
sound ARM updates for 5.12-rc1: 2021-02-22 14:27:07 -08:00
tools kasan: prefix global functions with kasan_ 2021-02-24 13:38:30 -08:00
usr arch: ia64: Remove rest of perfmon support 2021-01-22 12:12:20 +05:30
virt KVM/arm64 fixes for 5.11, take #2 2021-02-12 14:07:39 +00:00
.clang-format clang-format: Update with the latest for_each macro list 2021-01-29 15:00:23 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-02-21 17:23:56 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: dccp: move Gerrit Renker to CREDITS 2021-01-14 10:53:49 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS dmaengine updates for v5.12-rc1 2021-02-23 15:05:10 -08:00
Makefile clang-lto for v5.12-rc1 (part2) 2021-02-23 15:13:45 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 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.