From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [PATCH 1/5] page allocator: Always wake kswapd when restarting an allocation attempt after direct reclaim failed Date: Mon, 26 Oct 2009 10:11:29 +0900 (JST) Message-ID: <20091026100019.2F4A.A69D9226@jp.fujitsu.com> References: <1256221356-26049-1-git-send-email-mel@csn.ul.ie> <1256221356-26049-2-git-send-email-mel@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Cc: kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Frans Pop , Jiri Kosina , Sven Geggus , Karol Lewandowski , Tobias Oetiker , "Rafael J. Wysocki" , David Miller , Reinette Chatre , Kalle Valo , David Rientjes , Mohamed Abbas , Jens Axboe , "John W. Linville" , Pekka Enberg , Bartlomiej Zolnierkiewicz , Greg Kroah-Hartman , Stephan von Krawczynski , Kernel Testers List , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org\"" To: Mel Gorman Return-path: In-Reply-To: <1256221356-26049-2-git-send-email-mel-wPRd99KPJ+uzQB+pC5nmwQ@public.gmane.org> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org > If a direct reclaim makes no forward progress, it considers whether it > should go OOM or not. Whether OOM is triggered or not, it may retry the > application afterwards. In times past, this would always wake kswapd as well > but currently, kswapd is not woken up after direct reclaim fails. For order-0 > allocations, this makes little difference but if there is a heavy mix of > higher-order allocations that direct reclaim is failing for, it might mean > that kswapd is not rewoken for higher orders as much as it did previously. > > This patch wakes up kswapd when an allocation is being retried after a direct > reclaim failure. It would be expected that kswapd is already awake, but > this has the effect of telling kswapd to reclaim at the higher order as well. > > Signed-off-by: Mel Gorman > --- > mm/page_alloc.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index bf72055..dfa4362 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1817,9 +1817,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE) > goto nopage; > > +restart: > wake_all_kswapd(order, zonelist, high_zoneidx); > > -restart: > /* > * OK, we're below the kswapd watermark and have kicked background > * reclaim. Now things get more complex, so set up alloc_flags according I think this patch is correct. personally, I like to add some commnent at restart label. but it isn't big matter. Reviewed-by: KOSAKI Motohiro However, I have a question. __alloc_pages_slowpath() retry logic is, 1. try_to_free_pages() reclaimed some pages: -> wait awhile and goto rebalance 2. try_to_free_pages() didn't reclaimed any page: -> call out_of_memory() and goto restart Then, case-1 should be fixed too? I mean, diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bf72055..5a27896 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1899,6 +1899,12 @@ rebalance: if (should_alloc_retry(gfp_mask, order, pages_reclaimed)) { /* Wait for some write requests to complete then retry */ congestion_wait(BLK_RW_ASYNC, HZ/50); + + /* + * While we wait congestion wait, Amount of free memory can + * be changed dramatically. Thus, we kick kswapd again. + */ + wake_all_kswapd(order, zonelist, high_zoneidx); goto rebalance; } ------------------------------------------- ?