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j1STZZLyiWOV4Qs9QVX8p/VzqCLadp1k0HXePMFzhwwZhELXalhb89FROWMcfYdvcsIBjaRpEr4WTujwIRgyTIWf3PYxHqra1qWxEQSor8GXbzsg9+HlPiibIXPgtILxZgBMTOaBprrAmzv2f8mZGtx9iuWacoMAfVW2YfVI9qqbaA62gtTDVlTqU82PIevt0YPJB78e3rfk0OUOQHLATxMasGZIuZsggoaTpsmo9sMFgifJbCxEGZWp0XIsr5xOzwVz9MClyjio7SF/w0H1QwkYMEdiKraaQvrm+mV7LvZf/4ke75boUVEQxcZUm4/0otxY2S7sLvBQWnVK5iCnkc55gmHx06sBGbCtEcWwH3owGR+3zo8ktGMLskjMMguHWqDOw+5PWlqWZPNw9zdhsAm0Ag7m3OvZQ/ZGasa6Bol6eS2vHnpH3PHrQ3SmOQbPppl+CC9ObS9ms1mE= 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: 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. Regards Yin, Fengwei > > > Regards > Yin, Fengwei > >> >> Thanks. >