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 DB7991552F5 for ; Fri, 7 Feb 2025 06:28:13 +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=1738909698; cv=none; b=Yr+gNOq4nNa9KswjWfLdyYU9+DBjEenISh+Y1/khZOffIcYWmB2zJa0Pf+rqFIb1b+YOO7TjNmHKCQ10dRSkFJkLyvlUfz0ruNSz0myFkHGc6OWgJCoe/HaEus4OL7SHD9ktH7MaLJ9GRk7NLT/9m2Igh0DMaJJ/I9+98TxQIKo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738909698; c=relaxed/simple; bh=lYWhFvuV1qciqW9BNvk+T24o7MhzyOdEN6qRDw0hU1Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=d6Mx5+kRcAxgkKQcywsNztWQsO0cCwk5cUFan6IOgXhWShFXclxUBC++2f8D2ucvZWe8H1hd9U+WDIff5gdLGp8kb4lwMh0ro01J5GPe6TYY7jWoCwNXPMXaY4IfVdRuGqfPfiXCVd7f7FkTAGmwzKNBjPqldXqfelCApmTFYaw= 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=CG4e8Z+q; 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="CG4e8Z+q" 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=jb2l+oVbEpj/B+oQuY8QRQ8MFzZ4zeFis1BLttJBF9s=; b=CG4e8Z+qXX87bmmoXiwTcBS2Vp FnIHKiPPaLCWQYisJlXJcY3IzD77kMLWx3zgRvZ9AMQJb3BTc8vo2+s+gz3zxRb0WaKUgHAI1jvqn LbNQ2O4MjOeA0p/hZrHE0hWimZ+T/HFYFC4nCCKVAD9g0E9rTn3BwP+8kUW5XI748I9QtnRvWr5ri CIhWK6R8biADNYKZxdkD+5D1NlVY81lQ/Bk199v+tNkv3jokXgTs32rNqJenls8R/3AfYj9tM0GnH qWJvR5qUN87sIkG+yZcHGxU5yvEwZ1E/pPK+l7JPP4MBklU7ENXHuZ7gYQq5W2oPbT6KyizwLVHSq DBw5Jb/Q==; 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 1tgHqK-005gUB-1p; Fri, 07 Feb 2025 07:28:06 +0100 Message-ID: <612ce321-893a-468c-bbda-0220edab5036@igalia.com> Date: Fri, 7 Feb 2025 15:28:01 +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 1/2] sched_ext: Add an event, SCX_EV_ENQ_SLICE_DFL 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> <20250207031338.393045-2-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 Hi Andrea, On 25. 2. 7. 15:17, Andrea Righi wrote: > Hi Changwoo, > > On Fri, Feb 07, 2025 at 12:13:37PM +0900, Changwoo Min wrote: >> Add a core event, SCX_EV_ENQ_SLICE_DFL, which represents how many >> tasks have been enqueued (or pick_task-ed) with a default time slice >> (SCX_SLICE_DFL). >> >> 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. >> >> __scx_add_event() is used since the caller holds an rq lock, >> so the preemption has already been disabled. > > We may want to consider select_task_rq_scx() as well, when ops.select_cpu() > is not implemented (or during rq_bypass). > > In this case, if scx_select_cpu_dfl() finds an idle CPU, we implicitly > dispatch the task to the local DSQ with SCX_SLICE_DFL. You are right. I will add it too. Thanks! -- Changwoo