From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id EACE76B02F1 for ; Tue, 20 Dec 2016 07:31:24 -0500 (EST) Received: by mail-wm0-f72.google.com with SMTP id m203so24742621wma.2 for ; Tue, 20 Dec 2016 04:31:24 -0800 (PST) Received: from outbound-smtp03.blacknight.com (outbound-smtp03.blacknight.com. [81.17.249.16]) by mx.google.com with ESMTPS id km9si22453156wjb.282.2016.12.20.04.31.23 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 20 Dec 2016 04:31:23 -0800 (PST) Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp03.blacknight.com (Postfix) with ESMTPS id B85A099205 for ; Tue, 20 Dec 2016 12:31:22 +0000 (UTC) Date: Tue, 20 Dec 2016 12:31:22 +0000 From: Mel Gorman Subject: Re: [PATCH RFC 1/1] mm, page_alloc: fix incorrect zone_statistics data Message-ID: <20161220123121.e4wgkxm2txdoxogo@techsingularity.net> References: <1481522347-20393-1-git-send-email-hejianet@gmail.com> <1481522347-20393-2-git-send-email-hejianet@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1481522347-20393-2-git-send-email-hejianet@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jia He Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Vlastimil Babka , Michal Hocko , Johannes Weiner , Joonsoo Kim , Taku Izumi On Mon, Dec 12, 2016 at 01:59:07PM +0800, Jia He wrote: > In commit b9f00e147f27 ("mm, page_alloc: reduce branches in > zone_statistics"), it reconstructed codes to reduce the branch miss rate. > Compared with the original logic, it assumed if !(flag & __GFP_OTHER_NODE) > z->node would not be equal to preferred_zone->node. That seems to be > incorrect. > > Fixes: commit b9f00e147f27 ("mm, page_alloc: reduce branches in > zone_statistics") > > Signed-off-by: Jia He This is slightly curious. It appear it would only occur if a process was running on a node that was outside the memory policy. Can you confirm that is the case? If so, your patch is a a semantic curiousity because it's actually impossible for a NUMA allocation to be local and the definition of "HIT" is fuzzy enough to be useless. I won't object to the patch but it makes me trust "hit" even less than I already do for any analysis. Note that after this mail that I'll be unavailable by mail until early new years. -- Mel Gorman SUSE Labs -- 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/ . Don't email: email@kvack.org