From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACB5115FD13 for ; Fri, 7 Feb 2025 06:49:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.60.130.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738910978; cv=none; b=J0AOy0aUi8Sw7UBpNM8ioNpsC+PK0i9XidC21Uru8/Jj9WDBXmRvg9wFX6VsrkwivN/cJ8dVhMnsEyeI+vsZ6TSFxpaTYqtpkPPlynh4ruSFeLvQGuajT/LO3YIsdhhnmzcVIJ4Js/PKuBtSmOcl5mp5N7eFnL9bkB4ShqUa9og= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738910978; c=relaxed/simple; bh=Sj5i3eA+7EDHKM6zAxpLM+n6Y0z0oCg04XWj/RNF+QY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OIE5Z9lKOuG4X4nvtV79zr01AqV0zDIfys28RWenyP+3cFTP9g/L5Y6L3BTn2U9SS7bp1EzRx8WuxFG8VSGekKaL7Zsfa8jO9t18JjAYQNPB+zaTsF2ycNUMxjR5rF/+YGGlNIqnQ+w+CyGKDImIkE8muy+xNcBJn1Eyoz+4Opw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=HDpG4cX0; arc=none smtp.client-ip=178.60.130.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="HDpG4cX0" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=Y+c3RbgLLZ8Fjsx/qIA7GbI5CFeDrrguPRIE+c0Y74A=; b=HDpG4cX06h9+AslokoJp8LBsV5 szR5PQL/b7Z2gI65QMp0uXzDpk/wnrPEA8S92vKki10SYzj1XSDKsBJefxJVLC/3pJx/cY4Qw0r0q YHw4wAjkJKxOUv51A1gJkxwtHMwMrUeeVBDW51br8sihTaa29Wv91TpRIkNiKTp1Gp5leLwCVDb1w 4l1IxcqQPx6dTlpWoSQ4W31B0d+mfG2szZSWWrAhl723cYrlUHSto6f+e18kzqaagUo0QVYZ2TCkO 3abIWcppRQkZzQ4qGSecOiCZIg4ago1Iix2zT2OpuA1fEOipSEzxW1YWQC7kbsK9gkA7oh24qmFac X5PCPuMg==; Received: from [58.29.143.236] (helo=[192.168.1.6]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1tgIB1-005gnq-RV; Fri, 07 Feb 2025 07:49:29 +0100 Message-ID: <7623f8e9-d598-4c0f-8f65-5cb0cf563d4e@igalia.com> Date: Fri, 7 Feb 2025 15:49:24 +0900 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] sched_ext: Add a core event and update scx schedulers To: Andrea Righi Cc: tj@kernel.org, void@manifault.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org References: <20250207031338.393045-1-changwoo@igalia.com> From: Changwoo Min Content-Language: en-US, ko-KR, en-US-large, ko In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hello, On 25. 2. 7. 15:24, Andrea Righi wrote: > Hi, > > On Fri, Feb 07, 2025 at 12:13:36PM +0900, Changwoo Min wrote: >> This patchset introduces a new event, SCX_EV_ENQ_SLICE_DFL, and updates >> two scx schedulers -- scx_qmap and scx_central -- to print out the new >> event. >> >> SCX_EV_ENQ_SLICE_DFL counts how many times the tasks' time slice is set >> to the default value (SCX_SLICE_DFL) by the sched_ext core in the enqueue >> and pick_next paths. >> >> Scheduling a task with SCX_SLICE_DFL unintentionally would be a source >> of latency spikes because SCX_SLICE_DFL is relatively long (20 msec). >> Thus, soaring the SCX_EV_ENQ_SLICE_DFL value would be a sign of BPF >> scheduler bugs, causing latency spikes. > > Not directly related to this patch set, but as a general thought: would it > be useful to introduce ops->slice_ms (in sched_ext_ops) to override > SCX_SLICE_DFL? > > With that, schedulers that care about latency could set a smaller default > time slice to prevent potential spikes caused by the implicit use of > SCX_SLICE_DFL. > > Opinions? That sounds like a good idea! Regards, Changwoo Min