Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754771AbbLDBxl (ORCPT ); Thu, 3 Dec 2015 20:53:41 -0500 Received: from mga01.intel.com ([192.55.52.88]:6504 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754632AbbLDBxj (ORCPT ); Thu, 3 Dec 2015 20:53:39 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,378,1444719600"; d="scan'208";a="866307761" From: "Huang\, Ying" To: Mel Gorman Cc: Michal Hocko , lkp@01.org, LKML , Andrew Morton , Rik van Riel , Vitaly Wool , David Rientjes , Christoph Lameter , Johannes Weiner , Vlastimil Babka , Will Deacon , Linus Torvalds Subject: Re: [lkp] [mm, page_alloc] d0164adc89: -100.0% fsmark.app_overhead References: <20151126132511.GG14880@techsingularity.net> <87oaegmeer.fsf@yhuang-dev.intel.com> <20151127100647.GH14880@techsingularity.net> <87h9k4kzcv.fsf@yhuang-dev.intel.com> <20151202110009.GA2015@techsingularity.net> <20151202120046.GE25284@dhcp22.suse.cz> <20151202140845.GA19677@suse.de> <20151202141529.GG25284@dhcp22.suse.cz> <20151202144525.GC2015@techsingularity.net> <87k2ovyl4y.fsf@yhuang-dev.intel.com> <20151203101719.GG2015@techsingularity.net> Date: Fri, 04 Dec 2015 09:53:35 +0800 In-Reply-To: <20151203101719.GG2015@techsingularity.net> (Mel Gorman's message of "Thu, 3 Dec 2015 10:17:19 +0000") Message-ID: <87wpsvkmhs.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2789 Lines: 64 Mel Gorman writes: > On Thu, Dec 03, 2015 at 04:46:53PM +0800, Huang, Ying wrote: >> Mel Gorman writes: >> >> > On Wed, Dec 02, 2015 at 03:15:29PM +0100, Michal Hocko wrote: >> >> > > I didn't mention this allocation failure because I am not sure it is >> >> > > really related. >> >> > > >> >> > >> >> > I'm fairly sure it is. The failure is an allocation site that cannot >> >> > sleep but did not specify __GFP_HIGH. >> >> >> >> yeah but this was the case even before your patch. As the caller used >> >> GFP_ATOMIC then it got __GFP_ATOMIC after your patch so it still >> >> managed to do ALLOC_HARDER. I would agree if this was an explicit >> >> GFP_NOWAIT. Unless I am missing something your patch hasn't changed the >> >> behavior for this particular allocation. >> >> >> > >> > You're right. I think it's this hunk that is the problem. >> > >> > @@ -1186,7 +1186,7 @@ static struct request *blk_mq_map_request(struct >> > request_queue *q, >> > ctx = blk_mq_get_ctx(q); >> > hctx = q->mq_ops->map_queue(q, ctx->cpu); >> > blk_mq_set_alloc_data(&alloc_data, q, >> > - __GFP_WAIT|GFP_ATOMIC, false, ctx, hctx); >> > + __GFP_WAIT|__GFP_HIGH, false, ctx, hctx); >> > rq = __blk_mq_alloc_request(&alloc_data, rw); >> > ctx = alloc_data.ctx; >> > hctx = alloc_data.hctx; >> > >> > This specific path at this patch is not waking kswapd any more when it >> > should. A series of allocations there could hit the watermarks and never wake >> > kswapd and then be followed by an atomic allocation failure that woke kswapd. >> > >> > This bug gets fixed later by the commit 71baba4b92dc ("mm, page_alloc: >> > rename __GFP_WAIT to __GFP_RECLAIM") so it's not a bug in the current >> > kernel. However, it happens to break bisection and would be caught if each >> > individual commit was tested. >> > >> > Your __GFP_HIGH patch is still fine although not the direct fix for this >> > specific problem. Commit 71baba4b92dc is. >> > >> > Ying, does the page allocation failure messages happen when the whole >> > series is applied? i.e. is 4.4-rc3 ok? >> >> There are allocation errors for 4.4-rc3 too. dmesg is attached. >> > > What is the result of the __GFP_HIGH patch to give it access to > reserves? Applied Michal's patch on v4.4-rc3 and tested again, now there is no page allocation failure. Best Regards, Huang, Ying -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/