From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 003.mia.mailroute.net (003.mia.mailroute.net [199.89.3.6]) (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 0C53728850F; Thu, 9 Oct 2025 23:40:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.3.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760053228; cv=none; b=eQYVylonX4EE4s7EJapBCo8MhhgfKzx2NYIHXhwVygSu1kOhUCmey/+xtXINSvRVx7qeerX3KZuXqsOmoojitdTNzhogwWEgBdu+ZTGPw/OB1AWgsApEUbvDVeBeaDpmy4Wd02dgGAzVIavjc4LjZNnbCB4zWv1I7IgizkorNnI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760053228; c=relaxed/simple; bh=jbXf+oYCbVfnN9hCBEoXYickNFcUbhVgCGfXK6UgfYs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EliBa+lSXMIBYiVLpzcILH+CTdPJ++oOuuEj069A/FVFgqVKJXqZkqxxnOWblFonQ9dQpZ+shyTFKtZYz1244vPfba+RyI9t50J4JS0UGqSHf29meGMZEcdIgS+ckdaDI4KHFuxB0BMmHKHFKeHqIWuG7gjiEKiyO4zZgs5ySXQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org; spf=pass smtp.mailfrom=acm.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b=dSAyVX7V; arc=none smtp.client-ip=199.89.3.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=acm.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b="dSAyVX7V" Received: from localhost (localhost [127.0.0.1]) by 003.mia.mailroute.net (Postfix) with ESMTP id 4cjRFP75nDzltKFn; Thu, 9 Oct 2025 23:40:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:content-type:content-type:in-reply-to :from:from:content-language:references:subject:subject :user-agent:mime-version:date:date:message-id:received:received; s=mr01; t=1760053224; x=1762645225; bh=yTHDZEo4xkKcumLOfsHylHgL /jrJwym+SE4lLdqXNgY=; b=dSAyVX7VZCVHuOzIqDyd7VcdjRatL6Aozqzh9sIp sJtazL044OBVOflbfKOzza/CVOClB/cbBYwhWMyTy4zEwNUtpB1r6Z8yxx9nb7gP D+Af2eLm+l2orUmsjxGoPyZPNtdVmTE9AgbewybZcwOEs32iyhvNiQM0gOyxktwe P3ixyOdiT/gOjCtpDce3Ja1MZRKTE0DDkNJEpOR1QFtgSSOVxkrYsnKR7fm1aP1M 7F3+Pu2FK5CKuNnNIojW0AJblLqESFonsd4jRX5IOneXycDskWoefcykcU5gjCUB yUIRaZtKzlETwT/xwWP8TkXwabotz7nIUHj1WbKJFr0EyA== X-Virus-Scanned: by MailRoute Received: from 003.mia.mailroute.net ([127.0.0.1]) by localhost (003.mia [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id IxN8B9_CWxTr; Thu, 9 Oct 2025 23:40:24 +0000 (UTC) Received: from [192.168.51.14] (c-73-231-117-72.hsd1.ca.comcast.net [73.231.117.72]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 003.mia.mailroute.net (Postfix) with ESMTPSA id 4cjRFH0Lsdzlgqyn; Thu, 9 Oct 2025 23:40:18 +0000 (UTC) Message-ID: <8406f13d-d8be-4957-b1ec-6996f19d32e9@acm.org> Date: Thu, 9 Oct 2025 16:40:16 -0700 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] block/mq-deadline: adjust the timeout period of the per_prio->dispatch To: Damien Le Moal , chengkaitao , axboe@kernel.dk Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Chengkaitao References: <20251009155253.14611-1-pilgrimtao@gmail.com> Content-Language: en-US From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/9/25 1:21 PM, Damien Le Moal wrote: > There is still something bothering me with this: the request is added to the > dispatch list, and *NOT* to the fifo/sort list. So this should be considered as > a scheduling decision in itself, and __dd_dispatch_request() reflects that as > the first thing it does is pick the requests that are in the dispatch list > already. However, __dd_dispatch_request() also has the check: > > if (started_after(dd, rq, latest_start)) > return NULL; > > for requests that are already in the dispatch list. That is what does not make > sense to me. Why ? There is no comment describing this. And I do not understand > why we should bother with any time for requests that are in the dispatch list > already. These should be sent to the drive first, always. > > This patch seems to be fixing a problem that is introduced by the above check. > But why this check ? What am I missing here ? Is my conclusion from the above correct that there is agreement that the I/O priority should be ignored for AT HEAD requests and that AT HEAD requests should always be dispatched first? If so, how about merging the three per I/O priority dispatch lists into a single dispatch list and not to call started_after() at all for the dispatch list? Thanks, Bart.