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 B5D6B14E2CC; Tue, 10 Dec 2024 20:33:47 +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=1733862829; cv=none; b=fCVYCHIRhQWeKP9ivvFAz1UlfuV5smcB7fSqq5Bb6WNx5xpiRBkQiE8ZYgS39fSojdPgqUHtcD9SFiOyFDk6njU+WbccEeCUmNTbP489J/1zXVtXYCLsGkdklS18wDhEz73URw67OyYONdL3VFe5d2EoOd3p2RR3L7HhNhaJWWk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733862829; c=relaxed/simple; bh=gCX3Kg2zrlybcZgIZASFW4SayKABZoVZVYeRec8AoMM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MqVWXJw+EF0BC1bxx+nzmH0Yncg35n058HiJmXZ2nH8BB2HosGLry/gtJfXial1FH9F+eGNR1xCxb1QOhSepQA79Tq8VwH0xXAza3feZTjZnTWSTQ9oPrH4uCiHOPENwlMqPa3EafoHccqCX/j3YM8pLsXuuXuGFaPx4W9FlprU= 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=xtueQlW0; 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="xtueQlW0" Received: from localhost (localhost [127.0.0.1]) by 008.lax.mailroute.net (Postfix) with ESMTP id 4Y79Rn0vTSz6Cl4Pk; Tue, 10 Dec 2024 20:33:41 +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=1733862814; x=1736454815; bh=2U7gKiL8ugvTpuPKu/6BqFFj wbiz86mIkeXs667F/Yw=; b=xtueQlW0zQb/YC92NBgEyoOTPLXcUENDwUqPsOD9 29FuTLNbNGJbWz+Rh2H/39DS8uSKeJQOwD+0L9l7PvtUxojnZRFqciA+k21N2832 0V9Cb2qBqGAK0hGQdPxfHOfHl7Ly2d3940OgHKnCkRINo4FE3HNAjvF2bYybooQi 9pIZvPcQrswIyIqn5qkznsNgv5a6nMC4OfdVn2va91Xb0nu1C1ZOn1mdsjTFgvio TICGY+LnEGI1PHJaU/Wy1mTQx2/caGtCEtqoL22i+ZlrisjX2UtFunnkchXoj8gu VJ+xP69l09NdL4tJccpvxv+vBVP0kjFFuglCZEf9JOGOIA== 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 PhYZ8bO0RNb2; Tue, 10 Dec 2024 20:33:34 +0000 (UTC) Received: from [100.66.154.22] (unknown [104.135.204.82]) (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 4Y79Rc1LY2z6ClL94; Tue, 10 Dec 2024 20:33:31 +0000 (UTC) Message-ID: Date: Tue, 10 Dec 2024 12:33:31 -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, 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, "yukuai (C)" References: <20241209115522.3741093-1-yukuai1@huaweicloud.com> <20241209115522.3741093-2-yukuai1@huaweicloud.com> <6e384b29-50d2-64bd-0d08-fc0f086c1cbd@huaweicloud.com> <7081765f-28d7-f594-1221-6034b9e88899@huaweicloud.com> Content-Language: en-US From: Bart Van Assche In-Reply-To: <7081765f-28d7-f594-1221-6034b9e88899@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/9/24 10:22 PM, Yu Kuai wrote: > First of all, are we in the agreement that it's not acceptable to > sacrifice performance in the default scenario just to make sure > functional correctness if async_depth is set to 1? How much does this affect performance? If this affects performance significantly I agree that this needs to be fixed. > If so, following are the options that I can think of to fix this: > > 1) make async_depth read-only, if 75% tags will hurt performance in some > cases, user can increase nr_requests to prevent it. > 2) refactor elevator sysfs api, remove eq->sysfs_lock and replace it > with q->sysfs_lock, so deadline_async_depth_store() will be protected > against changing hctxs, and min_shallow_depth can be updated here. > 3) other options? Another option is to remove the ability to configure async_depth. If it is too much trouble to get the implementation right without causing regressions for existing workloads, one possibility is to remove support for restricting the number of asynchronous requests in flight. Thanks, Bart.