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c1afbd5de1
Moving v1 userspace eventfd handling into memcontrol-v1.c shrank struct
vmpressure from 112 to 24 bytes when CONFIG_MEMCG_V1 is disabled. This
moved memory_events_local[MEMCG_SWAP_FAIL] and the hot vmstats_percpu
pointer onto the same cacheline.
The stress-ng mremap stressor exercises MADV_PAGEOUT with swap disabled,
generating about 20 million MEMCG_SWAP_FAIL updates per 60-second run on a
176-CPU test system. Those writes bounce the line while memcg statistics
paths load vmstats_percpu.
Move cgwb_list into the existing alignment gap and cacheline-align
vmstats_percpu. This separates the pointer from the event counters
without increasing the size of struct mem_cgroup in the tested
configuration.
The blamed commit reduced median mremap throughput by 4.38% on the test
system with one socket. The patched kernel brings the performance to
within 0.5% of the parent which is within the observed boot-to-boot spread
(up to 1.2%).
Link: https://lore.kernel.org/20260817103835.2937733-1-usama.arif@linux.dev
Fixes:
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|---|---|---|
| .. | ||
| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| cxl | ||
| drm | ||
| dt-bindings | ||
| hyperv | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rv | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| ufs | ||
| vdso | ||
| video | ||
| xen | ||
| Kbuild | ||