Re: [linux-next:master] [mm/vmpressure] ea928e9e18: stress-ng.mremap.ops_per_sec 36.2% regression
Shakeel Butt <[email protected]>
| Newsgroups | dev.linux.lists.oe-lkp,org.kernel.vger.cgroups,org.kvack.linux-mm |
|---|---|
| Message-ID | <[email protected]> |
On Thu, Aug 13, 2026 at 09:16:22PM +0800, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed a 36.2% regression of stress-ng.mremap.ops_per_sec on:
>
> commit: ea928e9e18da682e9a5bc40aa862bff7ce5ae42e ("mm/vmpressure: move v1 userspace eventfd code into memcontrol-v1.c") https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
>
> in testcase: stress-ng
> version: stress-ng-x86_64-29ce10a2c-1_20260712
> with following parameters:
>
> nr_threads: 100%
> testtime: 60s
> test: mremap
> cpufreq_governor: performance
>
>
>
> config: x86_64-rhel-9.4 (CONFIG_MEMCG=y and CONFIG_MEMCG_V1 is not set)
> compiler: gcc-14
> test machine: 256 threads 4 sockets INTEL(R) XEON(R) PLATINUM 8592+ (Emerald Rapids) with 256G memory
>
> (please refer to attached dmesg/kmsg for entire log/backtrace)
>
Hi there,
Can you please test the following patch and see if it fixes the regression?
From 84c0b05b3bc5cf73ee66ead75aafb1ad684462c3 Mon Sep 17 00:00:00 2001
From: Shakeel Butt <[email protected]>
Date: Thu, 13 Aug 2026 09:38:28 -0700
Subject: [PATCH] memcg: keep vmstats_percpu off the memory_events[] cacheline
Signed-off-by: Shakeel Butt <[email protected]>
---
include/linux/memcontrol.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e78bc98ab229..e25d5b9a1db8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -246,8 +246,13 @@ struct mem_cgroup {
/* handle for "memory.swap.events" */
struct cgroup_file swap_events_file;
- /* memory.stat */
+ /* Read-mostly. */
struct memcg_vmstats *vmstats;
+ struct memcg_vmstats_percpu __percpu *vmstats_percpu;
+ int kmemcg_id;
+
+ /* Write-hot from here on; do not let it share with the above. */
+ CACHELINE_PADDING(_pad_);
/* memory.events */
atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS];
@@ -266,9 +271,6 @@ struct mem_cgroup {
#if BITS_PER_LONG < 64
seqlock_t socket_pressure_seqlock;
#endif
- int kmemcg_id;
-
- struct memcg_vmstats_percpu __percpu *vmstats_percpu;
#ifdef CONFIG_CGROUP_WRITEBACK
struct list_head cgwb_list;
--
2.53.0-Meta