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Message-ID: <20160524061724.GA8259@dhcp22.suse.cz> Date: Tue, 24 May 2016 08:17:25 +0200 From: Michal Hocko <mhocko@...nel.org> To: Hugh Dickins <hughd@...gle.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, 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 Mon 23-05-16 16:32:56, Hugh Dickins wrote: > On Mon, 23 May 2016, Andrew Morton wrote: > > 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? > > It's not correct. "retry" is reset to 0 each time around the > loop, and it's only a meaningful number to add on to nr_failed, in > the case when we've gone through the whole list: not in this "goto > out" case. You are right! I've missed that, my bad. > We could add another loop to count how many are left > when we hit -ENOMEM, and add that on to nr_failed; but I'm not > convinced that it's worth the bother. Agreed! Sorry about the noise! -- Michal Hocko SUSE Labs
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