From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 438DCC10F29 for ; Mon, 9 Mar 2020 15:42:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1464020578 for ; Mon, 9 Mar 2020 15:42:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1464020578 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A12AF6B0005; Mon, 9 Mar 2020 11:42:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 99C2E6B0006; Mon, 9 Mar 2020 11:42:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 88B326B0007; Mon, 9 Mar 2020 11:42:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0155.hostedemail.com [216.40.44.155]) by kanga.kvack.org (Postfix) with ESMTP id 6F6286B0005 for ; Mon, 9 Mar 2020 11:42:54 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 382A68248047 for ; Mon, 9 Mar 2020 15:42:54 +0000 (UTC) X-FDA: 76576241868.11.sound85_537fad081a22e X-HE-Tag: sound85_537fad081a22e X-Filterd-Recvd-Size: 3842 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Mon, 9 Mar 2020 15:42:53 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id C77DDAD07; Mon, 9 Mar 2020 15:42:51 +0000 (UTC) Subject: Re: [PATCH v7 7/7] mm/madvise: allow KSM hints for remote API To: Oleksandr Natalenko , Michal Hocko Cc: Minchan Kim , Andrew Morton , LKML , linux-mm , linux-api@vger.kernel.org, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Johannes Weiner , Shakeel Butt , John Dias , Joel Fernandes , Jann Horn , alexander.h.duyck@linux.intel.com, sj38.park@gmail.com, SeongJae Park References: <20200302193630.68771-1-minchan@kernel.org> <20200302193630.68771-8-minchan@kernel.org> <2a66abd8-4103-f11b-06d1-07762667eee6@suse.cz> <20200306134146.mqiyvsdnqty7so53@butterfly.localdomain> <20200309131117.anvyjszaigpoz2kp@butterfly.localdomain> <20200309150815.GR8447@dhcp22.suse.cz> <20200309151932.6sjwq6bucbu6zsea@butterfly.localdomain> From: Vlastimil Babka Message-ID: <34f812b8-df54-eaad-5cf0-335f07da55c6@suse.cz> Date: Mon, 9 Mar 2020 16:42:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200309151932.6sjwq6bucbu6zsea@butterfly.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 3/9/20 4:19 PM, Oleksandr Natalenko wrote: > On Mon, Mar 09, 2020 at 04:08:15PM +0100, Michal Hocko wrote: >> On Mon 09-03-20 14:11:17, Oleksandr Natalenko wrote: >> > On Fri, Mar 06, 2020 at 05:08:18PM +0100, Vlastimil Babka wrote: >> [...] >> > > Dunno, it's nice to react to signals quickly, for any proces that gets them, no? >> > >> > So, do you mean something like this? >> > >> > === >> > diff --git a/mm/ksm.c b/mm/ksm.c >> > index 363ec8189561..b39c237cfcf4 100644 >> > --- a/mm/ksm.c >> > +++ b/mm/ksm.c >> > @@ -849,7 +849,8 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma, >> > for (addr = start; addr < end && !err; addr += PAGE_SIZE) { >> > if (ksm_test_exit(vma->vm_mm)) >> > break; >> > - if (signal_pending(current)) >> > + if (signal_pending(current) || >> > + signal_pending(rcu_dereference(vma->vm_mm->owner))) >> > err = -ERESTARTSYS; >> > else >> > err = break_ksm(vma, addr); >> > === >> >> This is broken because mm might be attached to different tasks. >> AFAIU this check is meant to allow quick backoff of the _calling_ >> process so that it doesn't waste time when the context is killed >> already. I do not understand why should we care about any other context >> here? What is the actual problem this would solve? > > I agree with you, but still trying to understand what does Vlastimil mean > :). Well you wondered if we should stop caring about current, and I said that probably wouldn't be nice. As for caring about the other task, patch 3/7 does that for (MADV_COLD|MADV_PAGEOUT) so I just pointed out that the KSM case doesn't. AFAIU if we don't check the signals, we might be blocking the killed task from exiting? >> >> -- >> Michal Hocko >> SUSE Labs >> >