Messages in this thread | | | From | "Luck, Tony" <> | Subject | RE: [PATCH v9 2/3] x86/mce: Add per-bank CMCI storm mitigation | Date | Wed, 11 Oct 2023 17:23:54 +0000 |
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> IIRC, CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B was enabled in 0Day's > kernel config for quite a while, to force each funtion's start > address aligned on 64 bytes. Don't know if this has been changed > recently. > > Also I noticed the patch introduce a new per-cpu variable 'storm_desc", > if the function address is 64B aligned, then per-cpu data alignment > may be related.
If adding (removing, changing) per-cpu variables can cause 8% performance changes, then maybe there needs to be some way to insulate the builds from these side effects (as was done with the 64-byte function alignment). I've no ideas on how to achieve that :-(
"storm_desc" is a largish per-cpu variable at 1568 bytes. But that doesn't quite get it into the top 20.
In the config used for my kernel build, it does appear just before a bunch of interrupt related per-cpu variables. Those might be sensitive to alignment?
000000000001ff40 d smca_misc_banks_map 000000000001ff48 d bank_map 000000000001ff50 d threshold_banks 000000000001ff60 d storm_desc 0000000000020580 d tsc_adjust 00000000000205c0 d lapic_events 00000000000206c0 d vector_cleanup 0000000000020720 D __uv_cpu_info 0000000000020738 d ipi_mask
-Tony
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