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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1ppCAy-00DT6w-9I; Wed, 19 Apr 2023 18:05:04 +0000 Date: Wed, 19 Apr 2023 19:05:04 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: akpm@linux-foundation.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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230419175836.3857458-1-surenb@google.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2408E10002B X-Rspam-User: X-Stat-Signature: yekqjmshqdy3ghupbrqxh54zss5ktbbi X-HE-Tag: 1681927529-338702 X-HE-Meta: U2FsdGVkX1/qeWXmh9h14q788zN1YWRSik3D2FWKW4ICG//XClMPwhNnMvmo5DVE+HmaqRmT+NnsRdwowJJ0SjYaCP4REWwbAxyQIezmtjiKfGDpfbTAeS9AsD20cLdYIAwDcxFduiixC0fTPpw421Nb54VA3BrbuvVXuTbP0bNUbFv5wLQzvjQ/XX+lRimKcxIeNJgBlaimpF4pnEFKsHZl46RTLCXEcHwln9v5129KuctU6w4136BRWvjc9Ko+nMV5FNFtt43qv8WKKqFue+G49MQJpZQrXxi2CoEn+qn51x1oQsF/zsO5ttCGVN6zo4HsJDP5sh4astO+LXjfUqlDbWpPlOXOmuzixZRjcEuAR53UzPeA2VV4QHOq0PkLQWCy+sl4bjqxXUsWxEdunA5QYh5oK+CgmSXxNxHgA1zW3COFR5Oak/XbhQ2wmWc4Ot5UwluVSMjQ6B7I8LzrLk+FsoUEupCQs/u7E3W0Bs6K1U1J//LqhkurIIwPxDnCQbSYy6+Fy9XNjLs9CNW4ffUcmB6yqaJRKfZdWiSF/2sg4h00DdpflHFM8KmvsErVUkZa/ItEw+aHJvlchEWUgJ20VDtkNxXjO1lUO+I2teMPryqcH8cf+M/LLN9nEBqmyOm7GhtLu8bin6SfomI/n3uzvs5NWmuAHekH19WDlCQI/+6KAC3wqbq8HNO50VFfu9fWJSjrFz506Q1VtQNgOayV+cI+3NLEWlIPIObOzX3tfakGuyeDyggJDkXwS/aofZwJ9Cu8wmn6j8+LIfdS5xFNY/8SD4lzjZbKNp14g88z+CT3SB7qEiBI+awHk6gf/Xvo6v5kISC406ap3wBLWZ8Zypf/36piRxbY4Qq9dS8d5zPUVyYJCRxWcyts7+cwFF6QKLG00e9wFITs3CcjA0ag2oL4y2Owe0SbLnyyEX+5QGkbTdVwIu2tuX97HJS9c4nCqE9N7/5F5SUc9nF fSzaj4+I +ruuAdmS8W6uEJ4jxwFNIjz3valmZFKEQRZm7q2aBi3zbHRnEkdSJPjy7mzRQu6T99AQXJj95Mbvk800WXUGFmx8zAi5UL1QzXJdRHfxEhxUYUw6wDCD0nubL5NTeRWOqQF/T39CJAbAxBP9NRwjH7lxgWVOTUkpUiqB7pKWRJbkZ8XKZIQSbN3mh8kEQ+NfoVslnZraHEQlHLmJwE2yJGEpjoVAADeJdRS0C6vYImDGTQwoCyROtaGv3vRhuF7+o8Et4T2wXO8g/b52ELsOQxNkGdxzlCLQd8rwb 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 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 Reviewed-by: Matthew Wilcox (Oracle)