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[2003:cb:c705:7f00:8245:d031:7f8b:e004]) by smtp.gmail.com with ESMTPSA id h10-20020adffa8a000000b002ce3d3d17e5sm11577227wrr.79.2023.03.21.07.17.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Mar 2023 07:17:50 -0700 (PDT) Message-ID: <9c6f1e65-d460-8204-4ef6-bf76d1a78b58@redhat.com> Date: Tue, 21 Mar 2023 15:17:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v4 0/5] batched remove rmap in try_to_unmap_one() To: "Yin, Fengwei" , Andrew Morton Cc: linux-mm@kvack.org, willy@infradead.org, mike.kravetz@oracle.com, sidhartha.kumar@oracle.com, naoya.horiguchi@nec.com, jane.chu@oracle.com References: <20230313124526.1207490-1-fengwei.yin@intel.com> <20230313114900.96cfad6c3e4b684646f74e61@linux-foundation.org> From: David Hildenbrand Organization: Red Hat In-Reply-To: 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-Server: rspam04 X-Rspamd-Queue-Id: 4EB9820007 X-Stat-Signature: daw485nnp9apepwuei35gwuj8n6cz5ig X-HE-Tag: 1679408319-164602 X-HE-Meta: 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 5CbauQOf yVaE9Gm7M3BJAzLzW6LQdnJFG69ivaWBMHtJlS+mDlVoDnvgyZUGkbbJQbjBrA/+1tXwIuc0Y7BjrrPlTN/P0VI2urAsjWU8jYlLgpQwAs/Cjrhn7iv+TJrR5A2oY+4B+mJrdR/ZrRdmx6dN07K8I9jZKlPPwuJ5V7VS1Yfmd/AnfOwvHaB6cblNnS7RPb/lLED5IvjVMKt6gy7m4DRyWzWwjWVHNrLly9B6jjT8Wo0uSOipXVcKPbvo8CEdBvN5n6PA6VpFVk61CtqUfGeT/GWvsTKMO6J71ySl03jc/EJFj3+mjsv/bnYsws7Q+Xm/GMbuh4jdbloBskI7KiyyaMRHktVqA3r2KgoWm0QrKSlvQ5N3p00fdl5JzvWpgveRC++9wVQ5rzKkQMbb4CAfdTPoD5NNHoClownP3cN9KOOh/0proOnFRhGmMpt+hvcAJrBmBtt2X+JWGMGeCrsl0pXj4dujDSnWDJX5W 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 20.03.23 14:47, Yin, Fengwei wrote: > Hi Andrew, David, > > On 3/14/2023 11:09 AM, Yin Fengwei wrote: >> On 3/14/23 02:49, Andrew Morton wrote: >>> On Mon, 13 Mar 2023 20:45:21 +0800 Yin Fengwei wrote: >>> >>>> This series is trying to bring the batched rmap removing to >>>> try_to_unmap_one(). It's expected that the batched rmap >>>> removing bring performance gain than remove rmap per page. >>>> >>>> This series reconstruct the try_to_unmap_one() from: >>>>    loop: >>>>       clear and update PTE >>>>       unmap one page >>>>       goto loop >>>> to: >>>>    loop: >>>>       clear and update PTE >>>>       goto loop >>>>    unmap the range of folio in one call >>>> It is one step to always map/unmap the entire folio in one call. >>>> Which can simplify the folio mapcount handling by avoid dealing >>>> with each page map/unmap. >>>> >>>> ... >>>> >>>> For performance gain demonstration, changed the MADV_PAGEOUT not >>>> to split the large folio for page cache and created a micro >>>> benchmark mainly as following: >>> >>> Please remind me why it's necessary to patch the kernel to actually >>> performance test this?  And why it's proving so hard to demonstrate >>> benefits in real-world workloads? >>> >>> (Yes, this was touched on in earlier discussion, but I do think these >>> considerations should be spelled out in the [0/N] changelog). >> OK. What about add following in cover letter: >> " >>  The performance gain of this series can be demonstrated with large >>  folio reclaim. In current kernel, vmscan() path will be benefited by >>  the changes. But there is no workload/benchmark can show the exact >>  performance gain for vmscan() path as far as I am aware. >> >>  Another way to demonstrate the performance benefit is using >>  MADV_PAGEOUT which can trigger page reclaim also. The problem is that >>  MADV_PAGEOUT always split the large folio because it's not aware of >>  large folio for page cache currently. To show the performance benefit, >>  MADV_PAGEOUT is updated not to split the large folio. >> >>  For long term with wider adoption of large folio in kernel (like large >>  folio for anonymous page), MADV_PAGEOUT needs be updated to handle >>  large folio as whole to avoid splitting it always. >> " > I just want to check how I can move this work forward. Is it enough > by adding above message? Or still need some other work be done first? Thanks. I think Andrew can add that, no need to resend. But we should see more review (I'm fairly busy ...). -- Thanks, David / dhildenb