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bh=ZBUbOusq+sm0P5pmZB0m0ci+m3HFcOugwkBsLM2PR5Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=AbQoFTmRgLa+Lw57I/LL4SEMpmqg3FDZ1M7SQgVL2DDh/3hBNeuSWcf+7L2HL8kUf xb8bnASaAmnMSGIP58Ti6mu11cKV2jtrhYJzgdvBiQ5Hw9Y0vpvBepZ+oSOfbCie82 R1EbPOfzdBXhbcjDIDMOgf3Bp+IWRk2nhSHuXeV8= Date: Mon, 5 Dec 2022 13:03:59 -0800 From: Andrew Morton To: Kefeng Wang Cc: , , Subject: Re: [PATCH] mm: add cond_resched() in swapin_walk_pmd_entry() Message-Id: <20221205130359.2c81c5df0fb777cf55495a02@linux-foundation.org> In-Reply-To: <20221205140327.72304-1-wangkefeng.wang@huawei.com> References: <20221205140327.72304-1-wangkefeng.wang@huawei.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 437E8180017 X-Stat-Signature: gff6k9fy646amtugokazra8teimmd8gq X-Rspam-User: X-Spamd-Result: default: False [3.53 / 9.00]; IRL_BL_25(2.00)[52.25.139.140:received]; SUBJECT_HAS_UNDERSCORES(1.00)[]; MV_CASE(0.50)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; RCVD_NO_TLS_LAST(0.10)[]; BAYES_HAM(-0.07)[57.58%]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; DKIM_TRACE(0.00)[linux-foundation.org:+]; FROM_EQ_ENVFROM(0.00)[]; DMARC_NA(0.00)[linux-foundation.org]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; R_DKIM_ALLOW(0.00)[linux-foundation.org:s=korg]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; FROM_HAS_DN(0.00)[]; R_SPF_ALLOW(0.00)[+a:sin.source.kernel.org]; RCPT_COUNT_THREE(0.00)[4]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[] X-Rspamd-Server: rspam08 X-HE-Tag: 1670274244-284593 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 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.