From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 352B91384BF; Tue, 19 Nov 2024 07:44:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732002300; cv=none; b=LgN9+sUzqGTZI5uTbXAN2stSrN5hyr80ZkAGiS3fGOn2tRnKsR5EOKv20FQhIVmlOQXr+7TeBO6bSgKHqrk9/TcAtuNh2oh5ei4Ey/VIzXNj1EMkqtqPlp+trXy8OTF48A5f/SlIxjM2a6BOecq7Gvd2XUcgYczOFwxFYgmDErw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732002300; c=relaxed/simple; bh=iGNe3Q+wcKdvH8EIwnKew2LtX/mvNPzigSTnBHiGvtE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lTIG22LQfVGFfIc2d4jFP5W4VbPrvW3nm3Iyf7sbVyUY6dwDOk/dLL6XKs87teXqPMAPskGsAgPZhkOnV/QL2lEMMayvVRnlwUsgrWpfPrg47kmF21rw/fHsC5q6wnes6yOUtgd9wK7YJ2sNFHHP91d13RCfkHi1XYa6U7zO0og= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=byA5pXRZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="byA5pXRZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8094C4CED1; Tue, 19 Nov 2024 07:44:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732002299; bh=iGNe3Q+wcKdvH8EIwnKew2LtX/mvNPzigSTnBHiGvtE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=byA5pXRZSLRqtoXv6eDpATAYxN2mODJyygFhH1URdXnhyYvVvKgrrmjm9WzAPlYbv mxC/I04lYIil1kJWmmaDE5Ac8uF3d/LHvowsR50E9BsvS5gyNRsK96N7QjD1OZoruV siHyDkhjMxMJ4jsKO0h+v5y70I+h5ewWALf2SKdqxl8zOsoVIok/OnsXmh1Ld1F3Lf /itfKWnICWNjVt/rfY7D492WFF5MpqVilxZclZCbqnqdUCIDOGXONjcg9l+WSG26k1 DsrOVLg/QX/pKK9wmHSVU7G0F4mkMo9mX30z5Ubi6WH8szh1y18WebXI4//YXi4KPe U/KRdEE/c1Mhw== Message-ID: Date: Tue, 19 Nov 2024 16:44:57 +0900 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v16 12/26] block: Rework request allocation in blk_mq_submit_bio() To: Bart Van Assche , Jens Axboe Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, Christoph Hellwig , Jaegeuk Kim References: <20241119002815.600608-1-bvanassche@acm.org> <20241119002815.600608-13-bvanassche@acm.org> From: Damien Le Moal Content-Language: en-US Organization: Western Digital Research In-Reply-To: <20241119002815.600608-13-bvanassche@acm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/19/24 09:28, Bart Van Assche wrote: > Prepare for allocating a request from a specific hctx by making > blk_mq_submit_bio() allocate a request later. > > The performance impact of this patch on the hot path is small: if a > request is cached, one percpu_ref_get(&q->q_usage_counter) call and one > percpu_ref_put(&q->q_usage_counter) call are added to the hot path. > > Signed-off-by: Bart Van Assche The patch looks OK, but I cannot weight on if this is really a "small" impact on performance. Jens may want to run his perf setup with this to verify. -- Damien Le Moal Western Digital Research