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

[David Hildenbrand]

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