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[70.52.229.124]) by smtp.gmail.com with ESMTPSA id i16-20020a05620a405000b007468733cd1fsm4814337qko.58.2023.04.19.11.27.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Apr 2023 11:27:23 -0700 (PDT) Date: Wed, 19 Apr 2023 14:27:21 -0400 From: Peter Xu To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v3 1/1] mm: do not increment pgfault stats when page fault handler retries Message-ID: References: <20230419175836.3857458-1-surenb@google.com> MIME-Version: 1.0 In-Reply-To: <20230419175836.3857458-1-surenb@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Rspamd-Queue-Id: 29AFC140011 X-Rspamd-Server: rspam01 X-Stat-Signature: gxybr7djyqjp86zqyw6zgixmnknxpbqa X-HE-Tag: 1681928845-925183 X-HE-Meta: U2FsdGVkX19FdNpSrKhlQpQO51TxGltyExkf5gOgdrQHPBxVSq/FXoEP9Lf2eYWg8GRJRrVvUqWGEnebTXRQFqYBqLemaxc8IKOyOknlIxXvkpYFN630VW2VUqN3WXumIBAPP342dHC9YWKB8W2EXGlWnBZzOkl6zZpOJt88pbCgrrDy2nsJ3k7o1EpFupWZFtFssGwcXEiBQSDmk5/25knOead0E/VTGgAGaer2c5tT9H41d9o2s3fFJMoByAkwxkoOk04FReQygKNlg1a51ArDW2i62MaUHd9taRwxumgPSa1HJ1T83897nyjo1FGQfFuoO+wG/td6SNYQ85Z2YXIdqcNpEU1oPRqlQdEGwNL62vdfPgZSaDSr4eMJyBLoYmiAwNE8kDJYq5jjECbQRmYZOBZ1kJRaT7FOfRT1NrgCeXKBYIZDxjs1zy3QcTwGD6aQqPFnU/qMN8mSyrfGMPjTlSJon+WKYOYZ3e+l4gTGeBS5fCEbeLXB63ekm6kpZuGhpi81EtiAhy3/p6Iy5Le6bE4Yne+z7K/PCNzYfYf/iXkIPxohVh1jbfr/5e/8E1uSyh7jq65OTJXjjjCI0ZNTpgIoPRNYkLM1W5e+rWARkeSLgZ2GrBfn9RK65X4zqECgLnZNBq1oRmGbeNfQHy/Si7Kw+mWQZjvyWI/oy7WymEWIrFScNJN/Wk7zgV2lIgX4tGmPrcrygtkUrZ7JLgDPEAFvgfQJwotdT+EpxmZuAFgylXfONrUFLYNDbXiHco7hfxbes08w4aUDXwar3hj9Xr4rSn3Xk5Fg0j7TUyPBPdpoEr+BXtjh+HphF5PwRzBau/N5aQ0e8FSdlMKn2rFRJ/q3UWKZExt65gB0geI9ePlFzAW/MN+RJsfIFabjkszTyCJ5wJUOBZ47i0Eh4osljDKvawTDAwdZRECpDCC6L3kO1U2DzOmom7gGdxZYm32lgd88tSBDE/4qQjA Gg2hBwNG RvLf9bG4RbY5/AdCtbuRsK8+Z63Ipox7QvkI/rRNIkpxNK0DPRq3DRnVNxefXVRaDRjNPBaCPCFHdFtlQZNk/rYXZRrQz7vZuafaqcDmUDacqrObteAA8se8/4Y/ibBoXgwEGECSwWk8KPPlAUEdwWCNhOyl+SoznTx78zNd/CDodoInHbl/VucFvVHTvZljKlboYVL2u5+C02jPL+kyhQkqyPofHcC2HUSdwCtJUlA/LAGl39MmgaKODJzW5aieQkLAddrnpYbWauAAOmgs3r979qCqj4muCakhlKhUnD1RwAYLBLFsnJrX5g+FwXVEwTjvHB1bFBbS0ah+RL+zkTpijlIxUadgHhEqpK2d6KTxj2cXTqz1qs82enyPoun9TjZ8+d7Fo4CbokVzbTcwNCM0qTkTY62ib4G2J7px4MUtPz9CTnQpS6Tgq6odfcwnHXp8lLgu+SAe0JxjAefxpSMhNvDMHhayvyze5 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000065, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Apr 19, 2023 at 10:58:36AM -0700, Suren Baghdasaryan wrote: > If the page fault handler requests a retry, we will count the fault > multiple times. This is a relatively harmless problem as the retry paths > are not often requested, and the only user-visible problem is that the > fault counter will be slightly higher than it should be. Nevertheless, > userspace only took one fault, and should not see the fact that the > kernel had to retry the fault multiple times. > Move page fault accounting into mm_account_fault() and skip incomplete > faults which will be accounted upon completion. > > Fixes: d065bd810b6d ("mm: retry page fault when blocking on disk transfer") > Signed-off-by: Suren Baghdasaryan Acked-by: Peter Xu -- Peter Xu