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Yujie Liu 66f3fc7411 sched/numa: Fix the vma scan starving issue 
[ Upstream commit f22cde4371f3c624e947a35b075c06c771442a43 ]

Problem statement:
Since commit fc137c0dda ("sched/numa: enhance vma scanning logic"), the
Numa vma scan overhead has been reduced a lot.  Meanwhile, the reducing of
the vma scan might create less Numa page fault information.  The
insufficient information makes it harder for the Numa balancer to make
decision.  Later, commit b7a5b537c55c08 ("sched/numa: Complete scanning of
partial VMAs regardless of PID activity") and commit 84db47ca7146d7
("sched/numa: Fix mm numa_scan_seq based unconditional scan") are found to
bring back part of the performance.

Recently when running SPECcpu omnetpp_r on a 320 CPUs/2 Sockets system, a
long duration of remote Numa node read was observed by PMU events: A few
cores having ~500MB/s remote memory access for ~20 seconds.  It causes
high core-to-core variance and performance penalty.  After the
investigation, it is found that many vmas are skipped due to the active
PID check.  According to the trace events, in most cases,
vma_is_accessed() returns false because the history access info stored in
pids_active array has been cleared.

Proposal:
The main idea is to adjust vma_is_accessed() to let it return true easier.
Thus compare the diff between mm->numa_scan_seq and
vma->numab_state->prev_scan_seq.  If the diff has exceeded the threshold,
scan the vma.

This patch especially helps the cases where there are small number of
threads, like the process-based SPECcpu.  Without this patch, if the
SPECcpu process access the vma at the beginning, then sleeps for a long
time, the pid_active array will be cleared.  A a result, if this process
is woken up again, it never has a chance to set prot_none anymore.
Because only the first 2 times of access is granted for vma scan:
(current->mm->numa_scan_seq) - vma->numab_state->start_scan_seq) < 2 to be
worse, no other threads within the task can help set the prot_none.  This
causes information lost.

Raghavendra helped test current patch and got the positive result
on the AMD platform:

autonumabench NUMA01
                            base                  patched
Amean     syst-NUMA01      194.05 (   0.00%)      165.11 *  14.92%*
Amean     elsp-NUMA01      324.86 (   0.00%)      315.58 *   2.86%*

Duration User      380345.36   368252.04
Duration System      1358.89     1156.23
Duration Elapsed     2277.45     2213.25

autonumabench NUMA02

Amean     syst-NUMA02        1.12 (   0.00%)        1.09 *   2.93%*
Amean     elsp-NUMA02        3.50 (   0.00%)        3.56 *  -1.84%*

Duration User        1513.23     1575.48
Duration System         8.33        8.13
Duration Elapsed       28.59       29.71

kernbench

Amean     user-256    22935.42 (   0.00%)    22535.19 *   1.75%*
Amean     syst-256     7284.16 (   0.00%)     7608.72 *  -4.46%*
Amean     elsp-256      159.01 (   0.00%)      158.17 *   0.53%*

Duration User       68816.41    67615.74
Duration System     21873.94    22848.08
Duration Elapsed      506.66      504.55

Intel 256 CPUs/2 Sockets:
autonuma benchmark also shows improvements:

                                               v6.10-rc5              v6.10-rc5
                                                                         +patch
Amean     syst-NUMA01                  245.85 (   0.00%)      230.84 *   6.11%*
Amean     syst-NUMA01_THREADLOCAL      205.27 (   0.00%)      191.86 *   6.53%*
Amean     syst-NUMA02                   18.57 (   0.00%)       18.09 *   2.58%*
Amean     syst-NUMA02_SMT                2.63 (   0.00%)        2.54 *   3.47%*
Amean     elsp-NUMA01                  517.17 (   0.00%)      526.34 *  -1.77%*
Amean     elsp-NUMA01_THREADLOCAL       99.92 (   0.00%)      100.59 *  -0.67%*
Amean     elsp-NUMA02                   15.81 (   0.00%)       15.72 *   0.59%*
Amean     elsp-NUMA02_SMT               13.23 (   0.00%)       12.89 *   2.53%*

                   v6.10-rc5   v6.10-rc5
                                  +patch
Duration User     1064010.16  1075416.23
Duration System      3307.64     3104.66
Duration Elapsed     4537.54     4604.73

The SPECcpu remote node access issue disappears with the patch applied.

Link: https://lkml.kernel.org/r/20240827112958.181388-1-yu.c.chen@intel.com
Fixes: fc137c0dda ("sched/numa: enhance vma scanning logic")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Yujie Liu <yujie.liu@intel.com>
Reported-by: Xiaoping Zhou <xiaoping.zhou@intel.com>
Reviewed-and-tested-by: Raghavendra K T <raghavendra.kt@amd.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: "Chen, Tim C" <tim.c.chen@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-10-04 16:29:22 +02:00
arch xen: tolerate ACPI NVS memory overlapping with Xen allocated memory 2024-10-04 16:29:13 +02:00
block block: fix potential invalid pointer dereference in blk_add_partition 2024-10-04 16:29:01 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: xor - fix template benchmarking 2024-10-04 16:28:49 +02:00
Documentation ipmi: docs: don't advertise deprecated sysfs entries 2024-10-04 16:29:12 +02:00
drivers tpm: Clean up TPM space after command failure 2024-10-04 16:29:14 +02:00
fs ext4: check stripe size compatibility on remount as well 2024-10-04 16:29:21 +02:00
include sched/numa: Complete scanning of inactive VMAs when there is no alternative 2024-10-04 16:29:22 +02:00
init rust: fix the default format for CONFIG_{RUSTC,BINDGEN}_VERSION_TEXT 2024-08-29 17:33:29 +02:00
io_uring io_uring/io-wq: inherit cpuset of cgroup in io worker 2024-10-04 16:29:01 +02:00
ipc sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table) 2024-08-11 12:47:13 +02:00
kernel sched/numa: Fix the vma scan starving issue 2024-10-04 16:29:22 +02:00
lib xz: cleanup CRC32 edits from 2018 2024-10-04 16:29:19 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: avoid leaving partial pfn mappings around in error case 2024-09-18 19:24:07 +02:00
net ipv6: avoid possible NULL deref in rt6_uncached_list_flush_dev() 2024-10-04 16:28:59 +02:00
rust rust: kbuild: fix export of bss symbols 2024-09-12 11:11:32 +02:00
samples samples/bpf: Fix compilation errors with cf-protection option 2024-10-04 16:29:19 +02:00
scripts scripts: kconfig: merge_config: config files: add a trailing newline 2024-09-18 19:24:05 +02:00
security smackfs: Use rcu_assign_pointer() to ensure safe assignment in smk_set_cipso 2024-10-04 16:29:20 +02:00
sound ASoC: loongson: fix error release 2024-10-04 16:29:05 +02:00
tools selftests/bpf: Fix error compiling tc_redirect.c with musl libc 2024-10-04 16:29:19 +02:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
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 membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.53 2024-09-30 16:25:15 +02:00
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.