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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C5A2C6FD1D for ; Tue, 21 Mar 2023 12:27:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229788AbjCUM1o (ORCPT ); Tue, 21 Mar 2023 08:27:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230143AbjCUM1k (ORCPT ); Tue, 21 Mar 2023 08:27:40 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 009D63E635 for ; Tue, 21 Mar 2023 05:27:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uW6hcp6nJwytOeqeP4tIbrHPdMiAsq0Seo1YPugyfWc=; b=mJ0XuRIfQZsbhUGRZKXG2EU6LL 4f/Q/8rmiMU3YLJz5RySHpt+00wcIu/8FntV96d2to6aBPQupmAOTrg0AZ5rwjhex8hDZCRFIBu0k vqD99FxhVMMIKRHgmldR/ddu2/Q9XIAeYFuwDNJv4tl9VolqEjHT+XdZCZmcvQdgIm+OmYrJzJCbd P7z+OwFBkcgBGetJ8nPds8HtpPba+9nb0dAchByoFIo58gUr2LPGjEvbnUmpa7p9KdYFSkbmo7xRg hN8mwXTT7dZdhj4RY8FG3ClyOCr+xwa8cYkWfAM6lB2BrWuvpANA4Nk6SO1orNNIEnyHHy+tC/6+C 1niCWdhA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1peb4p-004Ffx-2m; Tue, 21 Mar 2023 12:26:56 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 06F3D30006D; Tue, 21 Mar 2023 13:26:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B6910240B24A5; Tue, 21 Mar 2023 13:26:53 +0100 (CET) Date: Tue, 21 Mar 2023 13:26:53 +0100 From: Peter Zijlstra To: Dietmar Eggemann Cc: Vincent Guittot , mingo@redhat.com, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, zhangqiao22@huawei.com Subject: Re: [PATCH v2] sched/fair: sanitize vruntime of entity being migrated Message-ID: <20230321122653.GJ2234901@hirez.programming.kicks-ass.net> References: <20230317160810.107988-1-vincent.guittot@linaro.org> <20230321100206.GE2234901@hirez.programming.kicks-ass.net> <7bba69e0-5261-9921-16b7-c8592b5d213b@arm.com> <20230321104949.GI2234901@hirez.programming.kicks-ass.net> <45741d41-3357-bffd-a244-954c32c9fe15@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45741d41-3357-bffd-a244-954c32c9fe15@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 21, 2023 at 12:13:06PM +0100, Dietmar Eggemann wrote: > On 21/03/2023 11:49, Peter Zijlstra wrote: > > On Tue, Mar 21, 2023 at 11:29:13AM +0100, Dietmar Eggemann wrote: > >> On 21/03/2023 11:02, Peter Zijlstra wrote: > >>> On Fri, Mar 17, 2023 at 05:08:10PM +0100, Vincent Guittot wrote: > >>>> Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed") > >>>> fixes an overflowing bug, but ignore a case that se->exec_start is reset > >>>> after a migration. > >>>> > >>>> For fixing this case, we delay the reset of se->exec_start after > >>>> placing the entity which se->exec_start to detect long sleeping task. > >>>> > >>>> In order to take into account a possible divergence between the clock_task > >>>> of 2 rqs, we increase the threshold to around 104 days. > >>>> > >>>> > >>>> Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed") > >>>> Signed-off-by: Zhang Qiao > >>>> Signed-off-by: Vincent Guittot > >>>> --- > >>> > >>> Blergh, this just isn't going to be nice. I'll go queue this for > >>> sched/urgent and then we can forget about this for a little while. > >>> > >>> Thanks! > >> > >> Don't we miss setting `se->exec_start = 0` for fair task in > >> move_queued_task()? ( ... and __migrate_swap_task()) > >> > >> https://lkml.kernel.org/r/df2cccda-1550-b06b-aa74-e0f054e9fb9d@arm.com > > > > Ah, I see what you mean now... When I read your and Vincent's replies > > earlier today I though you mean to avoid the extra ENQUEUE_MIGRATED use, > > but your actual goal was to capure more sites. > > > > Hmm, we could of course go add more ENQUEUE_MIGRATED, but you're right > > in that TASK_ON_RQ_MIGRATING already captures that. > > And in case of move_queued_task() this would have to be conditioned on > SCHED_NORMAL. I would prefer to not do that -- keep uniform rules. AFAICT the only other user of ENQUEUE_MIGRATED is deadline and that needs ENQUEUE_WAKEUP|ENQUEUE_MIGRATED combination to be effective and I don't think we've added any of those. > > An alternative is something like the below, that matches > > deactivate_task(), but still uses ENQUEUE_MIGRATED to pass it down into > > the class methods. > > > > Hmm? > > > > > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -2084,6 +2084,9 @@ static inline void dequeue_task(struct r > > > > void activate_task(struct rq *rq, struct task_struct *p, int flags) > > { > > + if (task_on_rq_migrating(p)) > > + flags |= ENQUEUE_MIGRATED; > > + > > enqueue_task(rq, p, flags); > > > > p->on_rq = TASK_ON_RQ_QUEUED; > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -8726,7 +8726,7 @@ static void attach_task(struct rq *rq, s > > lockdep_assert_rq_held(rq); > > > > WARN_ON_ONCE(task_rq(p) != rq); > > - activate_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_MIGRATED); > > + activate_task(rq, p, ENQUEUE_NOCLOCK); > > check_preempt_curr(rq, p, 0); > > } > > Would work too. OK, let me fold this in and then we can always tinker with it later if we're so motivated :-)