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[2003:cb:c70e:4f00:87ba:e9e9:3821:677b]) by smtp.gmail.com with ESMTPSA id y14-20020adff14e000000b002c59f18674asm14939888wro.22.2023.03.02.06.23.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 02 Mar 2023 06:23:47 -0800 (PST) Message-ID: Date: Thu, 2 Mar 2023 15:23:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 To: "Yin, Fengwei" , "akpm@linux-foundation.org" Cc: "linux-mm@kvack.org" , "willy@infradead.org" , "mike.kravetz@oracle.com" , "sidhartha.kumar@oracle.com" , "naoya.horiguchi@nec.com" , "chu, jane" References: <20230228122308.2972219-1-fengwei.yin@intel.com> <20230228122823.eba4f0fa5f7f436a2f8b3a3b@linux-foundation.org> <19263da54b9818332620345bbed69e8ded241e00.camel@intel.com> <604c372c-e474-14a7-dd80-c5197f12564d@redhat.com> <1c6c9d3e-3a7e-4d07-7c7c-9b7c01bcdac6@intel.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v2 0/5] batched remove rmap in try_to_unmap_one() In-Reply-To: <1c6c9d3e-3a7e-4d07-7c7c-9b7c01bcdac6@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: BA0951C000E X-Rspamd-Server: rspam01 X-Stat-Signature: p5mt7ob35sdzi9mgzanujhn8obkfsdt4 X-HE-Tag: 1677767031-240262 X-HE-Meta: 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 24J4WZIK mJyGSUDXN8df/i+c4HdkiHjQL1m988fYsO52y/nn7lOt7IWfujSgpgv6IaxrGH2btWyeRJrysoVdZCOR203TLTMMHysudgPEoU6R+9U9cPi/w25gQxuVdEUi9pUb8OfTY8KqKW1tnVeV9mKbqT4cr3nAGjP8girecwPkGUFpWBXLFx0MV4FZxWLtJ0i4IBnKt7x96vRmDeHrEPfvfTRf47VmSEOJezlagWnUsSkFQ+Rfxu+McFbdmXMWgQnzvWuGDKdWTx2mvoFE2MOQFzLL/4ksTstBCfS1McoFuMom9DCetNgNzeXOMovsNevaaxiobXeF3o+yx31EmrQvrPcPvT8HWheGDNtk6AQsEAMrkGlmi3O4IKCE672OgtMmGHk8pMCXRyGFErf1HV9RBZRjk+LXMzf+mSZaGycbX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 02.03.23 14:32, Yin, Fengwei wrote: > > > On 3/2/2023 6:04 PM, David Hildenbrand wrote: >> On 01.03.23 02:44, Yin, Fengwei wrote: >>> On Tue, 2023-02-28 at 12:28 -0800, Andrew Morton wrote: >>>> On Tue, 28 Feb 2023 20:23:03 +0800 Yin Fengwei >>>> wrote: >>>> >>>>> Testing done with the V2 patchset in a qemu guest >>>>> with 4G mem + 512M zram: >>>>>    - kernel mm selftest to trigger vmscan() and final hit >>>>>      try_to_unmap_one(). >>>>>    - Inject hwpoison to hugetlb page to trigger try_to_unmap_one() >>>>>      call against hugetlb. >>>>>    - 8 hours stress testing: Firefox + kernel mm selftest + kernel >>>>>      build. >>>> >>>> Was any performance testing done with these changes? >>> I tried to collect the performance data. But found out that it's >>> not easy to trigger try_to_unmap_one() path (the only one I noticed >>> is to trigger page cache reclaim). And I am not aware of a workload >>> can show it. Do you have some workloads suggsted to run? Thanks. >> >> If it happens barely, why care about performance and have a "398 insertions(+), 260 deletions(-)" ? > I mean I can't find workload to trigger page cache reclaim and measure > its performance. We can do "echo 1 > /proc/sys/vm/drop_caches" to reclaim > page cache. But there is no obvious indicator which shows the advantage > of this patchset. Maybe I could try eBPF to capture some statistic of > try_to_unmap_one()? If no workload/benchmark is affected (or simply corner cases where nobody cares about performance), I hope you understand that it's hard to argue why we should care about such an optimization then. I briefly thought that page migration could benefit, but it always uses try_to_migrate(). So I guess we're fairly limited to vmscan (memory failure is a corner cases). I recall that there are some performance-sensitive swap-to-nvdimm test cases. As an alternative, one could eventually write a microbenchmark that measures MADV_PAGEOUT performance -- it should also end up triggering vmscan, but only if the page is mapped exactly once (in which case, I assume batch removal doesn't really help ?). -- Thanks, David / dhildenb