From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AEB8419066B; Wed, 26 Jun 2024 17:56:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719424564; cv=none; b=jlAiKcouDP9mMGCvRRqhkUp2hyPa1ZqM9puPy3i8WRNaqG+jVipGlVEHpiA7mRJNn2ptVVCrvLL9fv9+5UQUYtG+AbP9dfwQV/IoULoPDrz5UAOlARw2tUQ1ttfNysqVMCSvR7cmxkMG13mLNUuUmERYGXGVPsZrEKzM356hwCM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719424564; c=relaxed/simple; bh=WCoPV67VMo5ajaQLAy72bRaJrigOMwbm9PqBFhY27aI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=U8tbDRmCZ6Yenlev04eqGBhlKBYdUzNk4q8ZluzxWGUuQAWYcxhFeHtTI+fPt+SJuPgfh1lbPIwfl32q4rF50ncQi9qoWajIJeVZNf6NbxDLXXjWqc1OpFAKY9UDlLDFM+/DzyyjjsV9Zrdey9bWzRP6J0uRPZcZC+j0WAt+GiE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=gdlGoQI0; arc=none smtp.client-ip=209.85.214.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gdlGoQI0" Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-1f8395a530dso54603045ad.0; Wed, 26 Jun 2024 10:56:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1719424562; x=1720029362; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=Shvv5DbIqP+jAT/jdjRlZNwu0Kg87TDqBKeTSC45xCo=; b=gdlGoQI0MwLnV1rNxIafCo6jF8ocwYrSPPU4FbdUYa66fCH1CPbh3UEtPAZXPInIas Zx4KTeosR8sX9w3mbkB5SVz6iv89RdA58I0BoBYPFmrRKR83vg728LFgIMQfqYck6235 xlw6eB1efEY4eoriVz2fft6yMPSLlPMCcWSEmInQiMThXf+wASAJyDspg6w0ZYIFgGqO iA/ubUehp6Ub/0J61QQDMq+w/gIx7W+raQB9SkPajZCu6KJi7KQ2PrxYLUZUjxis+VJK xFA7fvC6/E+dwccsHfm1wayE8/v5Os1HVbupkXQ2PrmosCTux+Afs1GEKC5Xucsx3yIA tfoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719424562; x=1720029362; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Shvv5DbIqP+jAT/jdjRlZNwu0Kg87TDqBKeTSC45xCo=; b=rjeqNrQuTohBeyPobmKgCnwnln5nxSKIMzN/g3KBbFqY6YBdx/7so9XICzVT38yiQj +lmvN0S0L17hnwzjly8HAPMeXzhyF21eW8phwVTaI86hoy85vtwOBj8NLyYYd29Qx8Jd lMXnM5kahWDZrgaPD5EPMTMHEU5CwTEfwOH38Vy/56MB9irsKc5BvQc7K778KxX8Vvkd SLqeEOeQdWbtuPaxhVng3TWq+nmitQVVQQ8iyHIbEzk4HU1C50OqgQLOlOArDyJQVYLs noorLqXbWXSEEpSSTAD2BMy2W7BbyWoZ7GFHYXilSyGDjZEJc0XJd9T985ftidS+gUdr o1qw== X-Forwarded-Encrypted: i=1; AJvYcCWjY/6mtKwoKcAoPfrf2ZXpSRXKpFfGvD7mXG/kyl4jxW3tX1Fo2svLomQPWwwptoT4nzAWK7iBJ/bxv/LBxsRTYxBijKflTStaKViaJh4rp4/4hQgnGJUIjdLslzXj8AKx X-Gm-Message-State: AOJu0YyajXBpoTGJl+vuD4hf5GOGpH/g1PTaUU4ecYSEIQT5+YMvIiTO YU1N9zMLPSYK+3lM+Zoh+2Sy1sdDL5nB3iEb7QkWi/Wp4bcnZ7z0 X-Google-Smtp-Source: AGHT+IE2+VTnd6IxHv8qGt5zGutsXo28ej0Kwi2W7W1x1xLZr3om4XkbBAhVSFXw9X/a3DP+xJqaGw== X-Received: by 2002:a17:902:ced2:b0:1fa:1f0c:f8fe with SMTP id d9443c01a7336-1fa23ee25famr120217565ad.32.1719424561792; Wed, 26 Jun 2024 10:56:01 -0700 (PDT) Received: from localhost (dhcp-141-239-159-203.hawaiiantel.net. [141.239.159.203]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f9eb1d448dsm102814395ad.0.2024.06.26.10.56.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Jun 2024 10:56:01 -0700 (PDT) Sender: Tejun Heo Date: Wed, 26 Jun 2024 07:56:00 -1000 From: Tejun Heo To: Peter Zijlstra Cc: Linus Torvalds , Thomas Gleixner , mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, joshdon@google.com, brho@google.com, pjt@google.com, derkling@google.com, haoluo@google.com, dvernet@meta.com, dschatzberg@meta.com, dskarlat@cs.cmu.edu, riel@surriel.com, changwoo@igalia.com, himadrics@inria.fr, memxor@gmail.com, andrea.righi@canonical.com, joel@joelfernandes.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH sched_ext/for-6.11] sched, sched_ext: Replace scx_next_task_picked() with sched_class->switch_class() Message-ID: References: <878qz0pcir.ffs@tglx> <20240624085927.GE31592@noisy.programming.kicks-ass.net> <20240625074935.GR31592@noisy.programming.kicks-ass.net> <20240626082848.GZ31592@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240626082848.GZ31592@noisy.programming.kicks-ass.net> Hello, On Wed, Jun 26, 2024 at 10:28:48AM +0200, Peter Zijlstra wrote: > I suppose I need to read more, because I'm not knowing what cpu_acquire > is :/ I do know I don't much like the asymmetry here, but maybe it makes > sense, dunno. The sched_ext ops are symmetric - ops.cpu_release() is called when SCX loses CPU to a higher priority sched class and ops.cpu_acquire() when the CPU returns to SCX afterwards. Where they hook into is not symmetric. The class which picks the next task already knows the previous task, so there's no need to add anything. However, without the new sched_class->switch_class(), the previous class has no way of knowing, so they're a bit different. Thanks. -- tejun