From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 991536B002D for ; Mon, 14 Nov 2011 21:08:38 -0500 (EST) Date: Tue, 15 Nov 2011 03:08:31 +0100 From: Andrea Arcangeli Subject: Re: [PATCH] mm: Do not stall in synchronous compaction for THP allocations Message-ID: <20111115020831.GF4414@redhat.com> References: <20111110100616.GD3083@suse.de> <20111110142202.GE3083@suse.de> <20111110161331.GG3083@suse.de> <20111110151211.523fa185.akpm@linux-foundation.org> <20111111100156.GI3083@suse.de> <20111114160345.01e94987.akpm@linux-foundation.org> <20111115020009.GE4414@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111115020009.GE4414@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Mel Gorman , Minchan Kim , Jan Kara , Andy Isaacson , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, Nov 15, 2011 at 03:00:09AM +0100, Andrea Arcangeli wrote: > I didn't fill that gap but I was reading the code again and I don't > see why we keep retrying for -EAGAIN in the !sync case. Maybe the > below is good (untested). I doubt it's good to spend cpu to retry the > trylock or to retry the migrate on a pinned page by O_DIRECT. In fact > as far as THP success rate is concerned maybe we should "goto out" > instead of "goto fail" but I didn't change to that as compaction even > if it fails a subpage may still be successful at creating order > 1/2/3/4...8 pages. I only avoid 9 loops to retry a trylock or a page > under O_DIRECT. Maybe that will save a bit of CPU, I doubt it can > decrease the success rate in any significant way. I'll test it at the > next build... At the same time also noticed another minor cleanup (also untested, will text at next build together with some other stuff). === From: Andrea Arcangeli Subject: [PATCH] compaction: move ISOLATE_CLEAN setting out of compaction_migratepages loop cc->sync and mode cannot change within the loop so move it out. Signed-off-by: Andrea Arcangeli --- mm/compaction.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 899d956..be0be1d 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -291,6 +291,9 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, return ISOLATE_ABORT; } + if (!cc->sync) + mode |= ISOLATE_CLEAN; + /* Time to isolate some pages for migration */ cond_resched(); spin_lock_irq(&zone->lru_lock); @@ -349,9 +352,6 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, continue; } - if (!cc->sync) - mode |= ISOLATE_CLEAN; - /* Try isolate the page */ if (__isolate_lru_page(page, mode, 0) != 0) continue; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org