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[151.227.74.206]) by smtp.gmail.com with ESMTPSA id u26sm5916793wrd.87.2019.10.18.07.48.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Oct 2019 07:48:25 -0700 (PDT) Date: Fri, 18 Oct 2019 15:48:24 +0100 From: Matt Fleming To: Mel Gorman Cc: Andrew Morton , Michal Hocko , Vlastimil Babka , Thomas Gleixner , Borislav Petkov , Linux-MM , Linux Kernel Mailing List Subject: Re: [PATCH 0/3] Recalculate per-cpu page allocator batch and high limits after deferred meminit Message-ID: <20191018144824.GI4065@codeblueprint.co.uk> References: <20191018105606.3249-1-mgorman@techsingularity.net> <20191018115849.GH4065@codeblueprint.co.uk> <20191018125449.GJ3321@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191018125449.GJ3321@techsingularity.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 18 Oct, at 01:54:49PM, Mel Gorman wrote: > On Fri, Oct 18, 2019 at 12:58:49PM +0100, Matt Fleming wrote: > > On Fri, 18 Oct, at 11:56:03AM, Mel Gorman wrote: > > > A private report stated that system CPU usage was excessive on an AMD > > > EPYC 2 machine while building kernels with much longer build times than > > > expected. The issue is partially explained by high zone lock contention > > > due to the per-cpu page allocator batch and high limits being calculated > > > incorrectly. This series addresses a large chunk of the problem. Patch 1 > > > is mostly cosmetic but prepares for patch 2 which is the real fix. Patch > > > 3 is definiely cosmetic but was noticed while implementing the fix. Proper > > > details are in the changelog for patch 2. > > > > > > include/linux/mm.h | 3 --- > > > mm/internal.h | 3 +++ > > > mm/page_alloc.c | 33 ++++++++++++++++++++------------- > > > 3 files changed, 23 insertions(+), 16 deletions(-) > > > > Just to confirm, these patches don't fix the issue we're seeing on the > > EPYC 2 machines, but they do return the batch sizes to sensible values. > > To be clear, does the patch a) fix *some* of the issue and there is > something else also going on that needs to be chased down or b) has no > impact on build time or system CPU usage on your machine? Sorry, I realise my email was pretty unclear. These patches *do* fix some of the issue because I no longer see as much contention on the zone locks with the patches applied.