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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 DE903C11F64 for ; Thu, 1 Jul 2021 16:28:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C0C31613E3 for ; Thu, 1 Jul 2021 16:28:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232661AbhGAQas (ORCPT ); Thu, 1 Jul 2021 12:30:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229978AbhGAQas (ORCPT ); Thu, 1 Jul 2021 12:30:48 -0400 Received: from mail-yb1-xb2f.google.com (mail-yb1-xb2f.google.com [IPv6:2607:f8b0:4864:20::b2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 987A1C061762 for ; Thu, 1 Jul 2021 09:28:16 -0700 (PDT) Received: by mail-yb1-xb2f.google.com with SMTP id g5so11737185ybu.10 for ; Thu, 01 Jul 2021 09:28:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jW9usmzYUneRtmPUUy8bPkIeD350ID0dCtIjd2wQbSQ=; b=nga6WacM6U52NLeH8VpfecsBjtdk02B2lXY37A1ANhERVcUSRWNPMz6NXXu3ZdKE2t xVdbc72ukqInAh1x/3KFXIMHUYfoIQKKBdL5KGYy0xhPAcebSQShwob41BY4D1Y+cTke 5j+IUh/1pu6ZaG5EcbEY0GNJ1EzcNVHbGBcKsftVHSHci4uVb1b+eHBeodvZP7Y9DF1+ 5lIgo6o4dzQFlw/x0ArhoVmeEtpr69uDijMGs04kDukeJ9JE1CrWJ+giAqa3DLFGsNA0 e04uxDISEgnhuWQN7/fF6LoZ7Y7vhbH4HdHYWrTH3RkJLs0GWQvkbimBCcGOqeVPdFOL JZDw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jW9usmzYUneRtmPUUy8bPkIeD350ID0dCtIjd2wQbSQ=; b=EQfTE6RcPa3kfIknxIo274F9pZ6nR4y5N3voA6ImsOWjjYYPT3t+NmBLNgKFJLvpni DHkops92muN0/wO1ny90lZTa3tdWdJmpmzBdxCO/BH7LBDMWND6pwLBmgRPh8QrfGDk+ wRD2PzLLD7i2hK9nA5uejHfVMUR45oBX5LEpVGwzRt+q/lj1rxWm1+DCje4Qy3IqU3Br kagGE1wBMgJ2L3axbdtOpAAAZqK0wjIwhltirAy5xByd4Y3ySp79xgCwTl7A8Oicwk/S afNbe3HHInQvgHl+d4Bnn3Q6+tKwWm+/ecTQRH7hqI9IX1qQBwF4JkucTPdgCEwtrxXj 06OA== X-Gm-Message-State: AOAM532QLQnY1Zg+ox1W8B9/lJZjlzsZJ+27iz2yMNVeZz3Iy0klg7Gd SJjsXXiKXr7TjUuh6CrblgoRjtBlbPWP+o1iXpR7vQ== X-Google-Smtp-Source: ABdhPJxJ105tQZtXJ2g6qDlXmogBaYsJLcJDXxQ5kncWGkCRYNQNcvRP9rBXNCvVZ0sAPG97Vogi4w7B9zdX140PCKE= X-Received: by 2002:a25:2e49:: with SMTP id b9mr836477ybn.250.1625156895472; Thu, 01 Jul 2021 09:28:15 -0700 (PDT) MIME-Version: 1.0 References: <20210630205151.137001-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 1 Jul 2021 09:28:04 -0700 Message-ID: Subject: Re: [PATCH v2 1/1] psi: stop relying on timer_pending for poll_work rescheduling To: Peter Zijlstra Cc: Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Benjamin Segall , Mel Gorman , Daniel Bristot de Oliveira , matthias.bgg@gmail.com, Minchan Kim , Tim Murray , YT Chang , =?UTF-8?B?V2VuanUgWHUgKOiuuOaWh+S4vik=?= , =?UTF-8?B?Sm9uYXRoYW4gSk1DaGVuICjpmbPlrrbmmI4p?= , LKML , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, kernel-team , SH Chen Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 1, 2021 at 9:12 AM Peter Zijlstra wrote: > > On Thu, Jul 01, 2021 at 09:09:25AM -0700, Suren Baghdasaryan wrote: > > On Thu, Jul 1, 2021 at 1:59 AM Peter Zijlstra wrote: > > > > > > On Wed, Jun 30, 2021 at 01:51:51PM -0700, Suren Baghdasaryan wrote: > > > > + /* cmpxchg should be called even when !force to set poll_scheduled */ > > > > + if (atomic_cmpxchg(&group->poll_scheduled, 0, 1) && !force) > > > > return; > > > > > > Why is that a cmpxchg() ? > > > > We want to set poll_scheduled and proceed with rescheduling the timer > > unless it's already scheduled, so cmpxchg helps us to make that > > decision atomically. Or did I misunderstand your question? > > What's wrong with: atomic_xchg(&group->poll_scheduled, 1) ? Yes, since poll_scheduled can be only 0 or 1 atomic_xchg should work fine here. Functionally equivalent but I assume atomic_xchg() is more efficient due to no comparison. Will respin v3 if the rest looks ok. > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >