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Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH] mm: add cond_resched() in swapin_walk_pmd_entry() Content-Language: en-US To: Andrew Morton CC: , , References: <20221205140327.72304-1-wangkefeng.wang@huawei.com> <20221205130359.2c81c5df0fb777cf55495a02@linux-foundation.org> From: Kefeng Wang In-Reply-To: <20221205130359.2c81c5df0fb777cf55495a02@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-Spamd-Result: default: False [0.28 / 9.00]; SUBJECT_HAS_UNDERSCORES(1.00)[]; DMARC_POLICY_ALLOW(-0.50)[huawei.com,quarantine]; R_SPF_ALLOW(-0.20)[+ip4:45.249.212.187/29]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; BAYES_HAM(-0.02)[49.88%]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; R_DKIM_NA(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; MID_RHS_MATCH_FROM(0.00)[]; HAS_XOIP(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; ARC_NA(0.00)[] X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 75C06A0002 X-Stat-Signature: 61kydtxbwwk531dzt7bqi3ei3x5nbajs X-HE-Tag: 1670290808-904527 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 2022/12/6 5:03, Andrew Morton wrote: > On Mon, 5 Dec 2022 22:03:27 +0800 Kefeng Wang wrote: > >> When handle MADV_WILLNEED in madvise(), the soflockup may be occurred >> in swapin_walk_pmd_entry() if swapin lots of memory on slow device, >> add a cond_resched() into it to avoid the possible softlockup. >> >> ... >> >> --- a/mm/madvise.c >> +++ b/mm/madvise.c >> @@ -226,6 +226,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, >> put_page(page); >> } >> swap_read_unplug(splug); >> + cond_resched(); >> >> return 0; >> } > I wonder if this would be better in walk_pmd_range(), to address other > very large walk attempts. mm/madvise.c:287:       walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma); mm/madvise.c:514:       walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private); mm/madvise.c:762:       walk_page_range(vma->vm_mm, range.start, range.end, mm/madvise.c-763-                       &madvise_free_walk_ops, &tlb); The cold_walk_ops and madvise_free_walk_ops are already with cond_resched() in theirs pmd_entry walk, maybe there's no need for a precautionary increase a cond_resched() for now > > .