Re: [PATCH memcg] mm/page_alloc.c: avoid statistic update with 0

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On 12.10.21 12:42, Vasily Averin wrote:
On 08.10.2021 14:47, Vlastimil Babka wrote:
On 10/8/21 11:24, Vasily Averin wrote:
__alloc_pages_bulk can call __count_zid_vm_events and zone_statistics
with nr_account = 0.

But that's not a bug, right? Just an effective no-op that's not commonly
happening, so is it worth the check?

Why not?

Yes, it's not a bug, it just makes the kernel a bit more efficient in a very unlikely case.
However, it looks strange and makes uninformed code reviewers like me worry about possible
problems inside the affected functions. No one else calls these functions from 0.

If it's not a BUG we'd better leave "Fixes:" tags away., it tends to confuse people looking for actual BUGs.

I'm also not sure if this micro-optimization is worth it. "bit more efficient in a very unlikely case" doesn't sound very compelling ... and personally I'd assume accounting functions can deal with a delta of 0.

--
Thanks,

David / dhildenb




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