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[70.53.122.15]) by smtp.gmail.com with ESMTPSA id y24sm1795095qtv.71.2020.08.27.07.15.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2020 07:15:50 -0700 (PDT) Date: Thu, 27 Aug 2020 10:15:49 -0400 From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: "Maya B . Gokhale" , Linus Torvalds , Yang Shi , Marty Mcfadden , Kirill Shutemov , Oleg Nesterov , Jann Horn , Jan Kara , Kirill Tkhai , Andrea Arcangeli , Christoph Hellwig , Andrew Morton Subject: Re: [PATCH 0/4] mm: Simplfy cow handling Message-ID: <20200827141549.GA6059@xz-x1> References: <20200821234958.7896-1-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200821234958.7896-1-peterx@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 81CAD180442D9 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Fri, Aug 21, 2020 at 07:49:54PM -0400, Peter Xu wrote: > This is a small series that I picked up from Linus's suggestion [0] to simplify > cow handling (and also more strict) by checking against page refcounts rather > than mapcounts. > > I'm CCing the author and reviewer of commit 52d1e606ee73 on ksm ("mm: reuse > only-pte-mapped KSM page in do_wp_page()", 2019-03-05). Please shoot if > there's any reason to keep the logic, or it'll be removed in this series. For > more information, please refer to [3,4]. > > The new mm counter in the last patch can be seen as RFC, depending on whether > anyone dislikes it... I used it majorly for observing the page reuses, so it is > kind of optional. > > Two tests I did: > > - Run a busy loop dirty program [1] that uses 6G of memory, restrict to 1G > RAM + 5G swap (cgroup). A few hours later, all things still look good. > Make sure to observe (still massive) correct page reuses using the new > counter using the last patch, probably when swapping in. > > - Run umapsort [2] to make sure uffd-wp will work again after applying this > series upon master 5.9-rc1 (5.9-rc1 is broken). > > In all cases, I must confess it's quite pleased to post a series with diffstat > like this... Hopefully this won't break anyone but only to make everything > better. > > Please review, thanks. > > [0] https://lore.kernel.org/lkml/CAHk-=wjn90-=s6MBerxTuP=-FVEZtR-LpoH9eenEQ3A-QfKTZw@mail.gmail.com > [1] https://github.com/xzpeter/clibs/blob/master/bsd/mig_mon/mig_mon.c > [2] https://github.com/LLNL/umap-apps/blob/develop/src/umapsort/umapsort.cpp > [3] https://lore.kernel.org/lkml/CAHk-=wh0syDtNzt9jGyHRV0r1pVX5gkdJWdenwmvy=dq0AL5mA@mail.gmail.com > [4] https://lore.kernel.org/lkml/CAHk-=wj5Oyg0LeAxSw_vizerm=sLd=sHfcVecZMKPZn6kNbbXA@mail.gmail.com Is there more comments for this series on either reviews, or suggested tests to carry out (before a broader trial)? Thanks, -- Peter Xu