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[91.12.104.112]) by smtp.gmail.com with ESMTPSA id q27sm6297872wrz.79.2021.05.28.02.03.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 May 2021 02:03:23 -0700 (PDT) Subject: Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs To: Mel Gorman , Dave Hansen Cc: Andrew Morton , Hillf Danton , Dave Hansen , Vlastimil Babka , Michal Hocko , LKML , Linux-MM , "Tang, Feng" References: <20210525080119.5455-1-mgorman@techsingularity.net> <7177f59b-dc05-daff-7dc6-5815b539a790@intel.com> <20210528085545.GJ30378@techsingularity.net> From: David Hildenbrand Organization: Red Hat Message-ID: <54ff0363-2f39-71d1-e26c-962c3fddedae@redhat.com> Date: Fri, 28 May 2021 11:03:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210528085545.GJ30378@techsingularity.net> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28.05.21 10:55, Mel Gorman wrote: > On Thu, May 27, 2021 at 12:36:21PM -0700, Dave Hansen wrote: >> Hi Mel, >> >> Feng Tang tossed these on a "Cascade Lake" system with 96 threads and >> ~512G of persistent memory and 128G of DRAM. The PMEM is in "volatile >> use" mode and being managed via the buddy just like the normal RAM. >> >> The PMEM zones are big ones: >> >> present 65011712 = 248 G >> high 134595 = 525 M >> >> The PMEM nodes, of course, don't have any CPUs in them. >> >> With your series, the pcp->high value per-cpu is 69584 pages or about >> 270MB per CPU. Scaled up by the 96 CPU threads, that's ~26GB of >> worst-case memory in the pcps per zone, or roughly 10% of the size of >> the zone. When I read about having such big amounts of free memory theoretically stuck in PCP lists, I guess we really want to start draining the PCP in alloc_contig_range(), just as we do with memory hotunplug when offlining. -- Thanks, David / dhildenb