linux-kernel - Re: [patch] mm, migrate: increment fail count on ENOMEM

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Date:	Mon, 23 May 2016 15:02:02 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Vlastimil Babka <vbabka@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] mm, migrate: increment fail count on ENOMEM

On Fri, 20 May 2016 15:31:21 +0200 Michal Hocko <mhocko@...nel.org> wrote:

> On Fri 20-05-16 15:19:12, Vlastimil Babka wrote:
> > On 05/20/2016 03:06 PM, Michal Hocko wrote:
> [...]
> > > Why don't we need also to count also retries?
> > 
> > We could, but not like you suggest.
> > 
> > > ---
> > > diff --git a/mm/migrate.c b/mm/migrate.c
> > > index 53ab6398e7a2..ef9c5211ae3c 100644
> > > --- a/mm/migrate.c
> > > +++ b/mm/migrate.c
> > > @@ -1190,9 +1190,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> > >   			}
> > >   		}
> > >   	}
> > > +out:
> > >   	nr_failed += retry;
> > >   	rc = nr_failed;
> > 
> > This overwrites rc == -ENOMEM, which at least compaction needs to recognize.
> > But we could duplicate "nr_failed += retry" in the case -ENOMEM.
> 
> Right you are. So we should do
> ---
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 53ab6398e7a2..123fed94022b 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1171,6 +1171,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  
>  			switch(rc) {
>  			case -ENOMEM:
> +				nr_failed += retry + 1;
>  				goto out;
>  			case -EAGAIN:
>  				retry++;
> 	
> 

argh, this was lost.  Please resend as a real patch sometime?

Thanks.