Re: [PATCH] MM: discard __GFP_ATOMIC

[NeilBrown]

On Fri, 19 Nov 2021, Mel Gorman wrote:
> On Thu, Nov 18, 2021 at 10:22:36AM +0100, Michal Hocko wrote:
> > [Cc Mel]
> > 
> 
> I think this patch should be ok. There are few direct users of __GFP_HIGH
> and some of them are borderline silly (e.g. mm/shmem.c specifying
> __GFP_HIGH|__GFP_NOMEMALLOC) while others just look questionable (
> drivers/md/raid10.c seems to assume __GFP_HIGH guarantees allocation
> success). Xen appears to be the worst abuser of __GFP_HIGH.

That __GFP_HIGH in raid10.c is passed to mempool_alloc(), so there is no
assumption that __GFP_HIGH will provide guarantees - the mempool does
that.
The comment - which I wrote 4 years ago and don't recall at all -
suggest it was purely about performance - get error handling out of the
way quickly.  I doubt I could justify it if challenged...

Thanks,
NeilBrown


> 
> -- 
> Mel Gorman
> SUSE Labs
> 
>