From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 008.lax.mailroute.net (008.lax.mailroute.net [199.89.1.11]) (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 AB2F213BAEE; Mon, 9 Dec 2024 18:03:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.1.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733767396; cv=none; b=M9Dj5a1Rv7PL2uQ4a7y08bcD2xgjNtN7pViCzQCP7jgwNjReLkWMZFBFrdFpE/j6xRjuIf229ijR5aWcofh77k3byNE7XrlF4R4aBZCWHYmTxiiah8+sYMyMlB4P8lRqB4SU/W+l49zQYj+ikv/C2BD0FXrymj8AK6BxYpY6wQQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733767396; c=relaxed/simple; bh=Xkf3rZcdNKIgI2QpssiA9RRjQfb0jQHBav21vRF0HlU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IEYT+6eGbFOEBaHzyZuX6u2Rw3gT1pzAvHpurkJEgIZ9Qxawz0lbawphE6zwZjOYGdOKqF0/BwcYmbsjnPdthFYhRArn7AqQhyMcJsXza/LQIh85LzcoTvEv5khLPBYYOROs0UPKRp7q1XOUelt7t5ArYEm/bMdGVNpKBWbrzrQ= 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=JxNxtaei; arc=none smtp.client-ip=199.89.1.11 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="JxNxtaei" Received: from localhost (localhost [127.0.0.1]) by 008.lax.mailroute.net (Postfix) with ESMTP id 4Y6V8X3vv5z6CmM6N; Mon, 9 Dec 2024 18:03:08 +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=1733767382; x=1736359383; bh=QyfTuLMhyhlY0D4S6FtpsgDx 2SCepf9ur753iNIB9Sk=; b=JxNxtaeieeSZDDtTLa0WCuED+PR6h93dfAINCUcu s0InJ1y5TttweQ5Z8kaLRsAS/U3ufKW3D/ZCA9R5bWVGfJ2L3jGQMVj1VC+isIjo 4mllyQABB2gKKUO01L4dc8DssnVSdnbl7V2ZtYGu3gg0jo7iBfL43Gwgz29DrLUK AzpGEd3Vwp8HgaympCrVzcouQkQF1svaC3z7QKABtmplr/ZkkNb/vzclDskM+UZM y4jOAO5MdaJASBTHMvtoUY+5BeKpiow2vEnrts58kyJqHP+ZX6xU3U+Q+kFxJwWl 5Cqlux3y2IUJmmf4Y8KftM/jzJuoK2d9fTFUBROaj7dkIw== X-Virus-Scanned: by MailRoute Received: from 008.lax.mailroute.net ([127.0.0.1]) by localhost (008.lax [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id DHC-zwyMc0Gc; Mon, 9 Dec 2024 18:03:02 +0000 (UTC) Received: from [192.168.50.14] (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 008.lax.mailroute.net (Postfix) with ESMTPSA id 4Y6V8J6Shfz6CmQtQ; Mon, 9 Dec 2024 18:02:56 +0000 (UTC) Message-ID: Date: Mon, 9 Dec 2024 10:02:54 -0800 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 RFC 1/3] block/mq-deadline: Revert "block/mq-deadline: Fix the tag reservation code" To: Yu Kuai , axboe@kernel.dk, akpm@linux-foundation.org, yang.yang@vivo.com, ming.lei@redhat.com, yukuai3@huawei.com, osandov@fb.com, paolo.valente@linaro.org Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com References: <20241209115522.3741093-1-yukuai1@huaweicloud.com> <20241209115522.3741093-2-yukuai1@huaweicloud.com> Content-Language: en-US From: Bart Van Assche In-Reply-To: <20241209115522.3741093-2-yukuai1@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/9/24 7:55 PM, Yu Kuai wrote: > From: Yu Kuai > > This reverts commit 39823b47bbd40502632ffba90ebb34fff7c8b5e8. > > Because tag reservation is not fixed and will introduce performance > problem. As explained in detail in the patch description and in the comments added by that patch, commit 39823b47bbd4 ("block/mq-deadline: Fix the tag reservation code") fixes broken code. So reverting that commit is wrong. I think that patches 1/3 and 3/3 of this series should be combined into a single patch. > 1) Set min_shallow_depth to 1 will end up setting wake_batch to 1, > deadline has no reason to do this. And this will cause performance > degradation in some high concurrency test, for both IO bandwidth > and cpu usage. As explained in the commit message, this is done because min_shallow_depth must be less than or equal to shallow_depth. Additionally, mq-deadline is not the only I/O scheduler that sets min_shallow_depth to 1. BFQ does this too. > 2) async_depth is nr_requests, hence shallow_depth will always set to > 1 << bt->sb.shift. For consequence, no tag can be reserved. This is not correct. dd->async_depth can be modified via sysfs. Bart.