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b=vn1AoCnzJnoc9nRWUm1XYMNe8Z6ktFUCQR7/S4ftimY6eUPldKv2/CFSSvKROT8GmER7/zl6MIVUJpxpYDI29Ownd0Lel3/D1tUQE66WFj1ycPpAeVaFRl7tk40v4+xuYt2ytZBFk99tQKDUFrJfrGlMpSnqJ7S0BKozkS/E6/U= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam011083073210;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=27;SR=0;TI=SMTPD_---0XAeSzYm_1788944341; Received: from 30.74.144.119(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XAeSzYm_1788944341 cluster:ay36) by smtp.aliyun-inc.com; Wed, 09 Sep 2026 16:59:02 +0800 Message-ID: Date: Wed, 9 Sep 2026 16:59:00 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 05/19] selftests/mm: make the swap cases' swapout reliable To: Kiryl Shutsemau , akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, rppt@kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, usama.anjum@arm.com, usama.arif@linux.dev, nico.pache@linux.dev, ziy@nvidia.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, vbabka@kernel.org, agordeev@linux.ibm.com, jgg@ziepe.ca, leon@kernel.org, kernel-team@meta.com, "Kiryl Shutsemau (Meta)" References: <20260908125105.1510704-1-kirill@shutemov.name> <20260908125105.1510704-6-kirill@shutemov.name> From: Baolin Wang In-Reply-To: <20260908125105.1510704-6-kirill@shutemov.name> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4D5D480002 X-Stat-Signature: cc7fe16df8kodrhxjdxwwgcusjzzkpfs X-HE-Tag: 1788944346-52312 X-HE-Meta: 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 Atq+a6+f lMD2HHfbhXABUW8+lmmiNvWPap2roPkTn9SpdzaLW0DdRQGvW10YoSek0xxf4jFAXXr267nMIZn13mIoMApPh/Yz82Xq2t+VGnXUqS9G4Pxf+F9sUmgOrPLj2nUo3zq1fMr0sBucODDVUnkYpQF1NiBGuMLF8EWQ9LX6aEDUeIxn25QFYStY1WV39Uh/WkXmoK8ZSSSq/4W9azI/Cwc+wrNK6leQQeeSCbaDiMS8624aIKkawRDrerVmcGxNo9tw0EDggLab0K0l6/Nr7wC3dtpW2OqEhAnjlyKGM9n6A2UJTPTKs0rR1VVEf6XYMaKInjpPXGKIIKDcuLnT7IxfSUVnNpcPdirIUqNuY8ycqa/ftq0T0NcT1dsAxD6IMYu7Vuoku Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/8/26 8:50 PM, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > collapse_swapin_single_pte() and collapse_max_ptes_swap() swap a range out > and then require smaps to report exactly the count they asked for. Two > things keep that count from arriving. > > MADV_PAGEOUT is best effort, so the count often turns up a moment late. > > And wait_for_scan() leaves the range eligible for collapsing, so > khugepaged is still working on it. Collapsing reads the swapped-out pages > back in, so the daemon empties the swap as fast as the case fills it. On > arm64 with 64K pages max_ptes_swap is 1024 pages, which is 64M a step, and > the case loses the race: > > # Swapout 1024 of 8192 pages... Fail > not ok 10 collapse_max_ptes_swap > > Retry for up to two seconds, holding the range out of khugepaged's reach > meanwhile. The collapse each case runs next restores MADV_HUGEPAGE, so > only the setup is affected. > > If the pages still won't swap out, skip: no swap, swap too small or full, > a memcg cap or busy writeback. None of that is a kernel bug. > > Assisted-by: LLM > Reviewed-by: Muhammad Usama Anjum > Tested-by: Muhammad Usama Anjum > Signed-off-by: Kiryl Shutsemau (Meta) > --- Make sense to me. So Reviewed-by: Baolin Wang