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Mel Gorman 8b10b465d0 mm/page_alloc: free pages in a single pass during bulk free 
free_pcppages_bulk() has taken two passes through the pcp lists since
commit 0a5f4e5b45 ("mm/free_pcppages_bulk: do not hold lock when
picking pages to free") due to deferring the cost of selecting PCP lists
until the zone lock is held.  Now that list selection is simplier, the
main cost during selection is bulkfree_pcp_prepare() which in the normal
case is a simple check and prefetching.  As the list manipulations have
cost in itself, go back to freeing pages in a single pass.

The series up to this point was evaulated using a trunc microbenchmark
that is truncating sparse files stored in page cache (mmtests config
config-io-trunc).  Sparse files were used to limit filesystem
interaction.  The results versus a revert of storing high-order pages in
the PCP lists is

1-socket Skylake
                               5.17.0-rc3             5.17.0-rc3             5.17.0-rc3
                                  vanilla      mm-reverthighpcp-v1     mm-highpcpopt-v2
 Min       elapsed      540.00 (   0.00%)      530.00 (   1.85%)      530.00 (   1.85%)
 Amean     elapsed      543.00 (   0.00%)      530.00 *   2.39%*      530.00 *   2.39%*
 Stddev    elapsed        4.83 (   0.00%)        0.00 ( 100.00%)        0.00 ( 100.00%)
 CoeffVar  elapsed        0.89 (   0.00%)        0.00 ( 100.00%)        0.00 ( 100.00%)
 Max       elapsed      550.00 (   0.00%)      530.00 (   3.64%)      530.00 (   3.64%)
 BAmean-50 elapsed      540.00 (   0.00%)      530.00 (   1.85%)      530.00 (   1.85%)
 BAmean-95 elapsed      542.22 (   0.00%)      530.00 (   2.25%)      530.00 (   2.25%)
 BAmean-99 elapsed      542.22 (   0.00%)      530.00 (   2.25%)      530.00 (   2.25%)

2-socket CascadeLake
                               5.17.0-rc3             5.17.0-rc3             5.17.0-rc3
                                  vanilla    mm-reverthighpcp-v1       mm-highpcpopt-v2
 Min       elapsed      510.00 (   0.00%)      500.00 (   1.96%)      500.00 (   1.96%)
 Amean     elapsed      529.00 (   0.00%)      521.00 (   1.51%)      510.00 *   3.59%*
 Stddev    elapsed       16.63 (   0.00%)       12.87 (  22.64%)       11.55 (  30.58%)
 CoeffVar  elapsed        3.14 (   0.00%)        2.47 (  21.46%)        2.26 (  27.99%)
 Max       elapsed      550.00 (   0.00%)      540.00 (   1.82%)      530.00 (   3.64%)
 BAmean-50 elapsed      516.00 (   0.00%)      512.00 (   0.78%)      500.00 (   3.10%)
 BAmean-95 elapsed      526.67 (   0.00%)      518.89 (   1.48%)      507.78 (   3.59%)
 BAmean-99 elapsed      526.67 (   0.00%)      518.89 (   1.48%)      507.78 (   3.59%)

The original motivation for multi-passes was will-it-scale page_fault1
using $nr_cpu processes.

2-socket CascadeLake (40 cores, 80 CPUs HT enabled)
                                                     5.17.0-rc3                 5.17.0-rc3
                                                        vanilla           mm-highpcpopt-v2
 Hmean     page_fault1-processes-2        2694662.26 (   0.00%)      2695780.35 (   0.04%)
 Hmean     page_fault1-processes-5        6425819.34 (   0.00%)      6435544.57 *   0.15%*
 Hmean     page_fault1-processes-8        9642169.10 (   0.00%)      9658962.39 (   0.17%)
 Hmean     page_fault1-processes-12      12167502.10 (   0.00%)     12190163.79 (   0.19%)
 Hmean     page_fault1-processes-21      15636859.03 (   0.00%)     15612447.26 (  -0.16%)
 Hmean     page_fault1-processes-30      25157348.61 (   0.00%)     25169456.65 (   0.05%)
 Hmean     page_fault1-processes-48      27694013.85 (   0.00%)     27671111.46 (  -0.08%)
 Hmean     page_fault1-processes-79      25928742.64 (   0.00%)     25934202.02 (   0.02%) <--
 Hmean     page_fault1-processes-110     25730869.75 (   0.00%)     25671880.65 *  -0.23%*
 Hmean     page_fault1-processes-141     25626992.42 (   0.00%)     25629551.61 (   0.01%)
 Hmean     page_fault1-processes-172     25611651.35 (   0.00%)     25614927.99 (   0.01%)
 Hmean     page_fault1-processes-203     25577298.75 (   0.00%)     25583445.59 (   0.02%)
 Hmean     page_fault1-processes-234     25580686.07 (   0.00%)     25608240.71 (   0.11%)
 Hmean     page_fault1-processes-265     25570215.47 (   0.00%)     25568647.58 (  -0.01%)
 Hmean     page_fault1-processes-296     25549488.62 (   0.00%)     25543935.00 (  -0.02%)
 Hmean     page_fault1-processes-320     25555149.05 (   0.00%)     25575696.74 (   0.08%)

The differences are mostly within the noise and the difference close to
$nr_cpus is negligible.

Link: https://lkml.kernel.org/r/20220217002227.5739-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Aaron Lu <aaron.lu@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.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>
2022-03-22 15:57:06 -07:00
arch cma: factor out minimum alignment requirement 2022-03-22 15:57:05 -07:00
block fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto crypto: af_alg - get rid of alg_memory_allocated 2022-02-15 14:29:04 +00:00
Documentation fs: introduce alloc_inode_sb() to allocate filesystems specific inode 2022-03-22 15:57:03 -07:00
drivers mm: enforce pageblock_order < MAX_ORDER 2022-03-22 15:57:06 -07:00
fs mm: dcache: use kmem_cache_alloc_lru() to allocate dentry 2022-03-22 15:57:03 -07:00
include mm: enforce pageblock_order < MAX_ORDER 2022-03-22 15:57:06 -07:00
init lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() 2022-01-22 08:33:37 +02:00
ipc fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
kernel cma: factor out minimum alignment requirement 2022-03-22 15:57:05 -07:00
lib xarray: use kmem_cache_alloc_lru to allocate xa_node 2022-03-22 15:57:03 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/page_alloc: free pages in a single pass during bulk free 2022-03-22 15:57:06 -07:00
net fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
samples samples/seccomp: Adjust sample to also provide kill option 2022-02-10 19:09:12 -08:00
scripts scripts/spelling.txt: add more spellings to spelling.txt 2022-03-22 15:57:00 -07:00
security selinux/stable-5.17 PR 20220223 2022-02-23 17:19:55 -08:00
sound ALSA: intel_hdmi: Fix reference to PCM buffer address 2022-03-02 09:25:37 +01:00
tools selftests, x86: fix how check_cc.sh is being invoked 2022-03-22 15:57:04 -07:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt KVM: Fix lockdep false negative during host resume 2022-02-17 09:52:50 -05:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap MAINTAINERS: Update Jisheng's email address 2022-03-08 17:30:32 +01:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
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 Add Paolo Abeni to networking maintainers 2022-03-15 12:16:10 -07:00
Makefile Linux 5.17 2022-03-20 13:14:17 -07:00
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.