From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 013.lax.mailroute.net (013.lax.mailroute.net [199.89.1.16]) (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 A3D94238150; Fri, 8 May 2026 16:11:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.1.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778256702; cv=none; b=PJD3IDnHhLZfdjXLfPsUBB/96JEBKMolQwTCmfbrGV/YmUuzNqttLmejSjSM6VCAVILMYs3E3PCSglFBnNsJSSrl0PoQwPuvqxG//1L3MPdodaWOJdweYZph2HTGb2CBoWPznaQvLJZllEGLmb1CwH+DhEvao3b+r0mRi3uEfa4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778256702; c=relaxed/simple; bh=cayfImqDZTr/xc0puxBpOA53TgBhP3tBGh1yXq7u9hM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=e3/foGyMsmzTxFfNWyc94ksNkDx9dQ5TbZgciRPi6mjxFQ5sm3mQ7gqtpI2j92lzV+jMUT4nMkqj7ttjIzUKIGSdaY+uL0JkXQ/Vh/cFA9HZrX6vtEgNKijfgoOa6ke3ExrfdC+i5Zc9Y/A76P2OCYf4ddRLJkxJ+uCyotzrvzk= 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=In0gZNPA; arc=none smtp.client-ip=199.89.1.16 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="In0gZNPA" Received: from localhost (localhost [127.0.0.1]) by 013.lax.mailroute.net (Postfix) with ESMTP id 4gBvJ56QjXzlfwHM; Fri, 8 May 2026 16:11:33 +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=1778256688; x=1780848689; bh=C1mrCW2xfduLae4ExxVch3Wb mSvTUGAOgl33Q2rkdjs=; b=In0gZNPAny4m6CXjaiQTjN71VXFx07RsCnmqU37G 9woPl6vCtRYlaOj0zxrFaVMD+NalMMTKfExRyWwwwqJ65iC/czeoaD4TveEgh6xX WgILO1YGUO+pxeiC2z8wh6H8qD9iegCk3SBEMZPY2Bl8E6txqBJmzzV/3Rksye2/ oRCIDgpmcrt4Z51Tpq03LoUAH4r5eQoZopLWfH1tNttMRRLlLRnovg/vKYz4MKcM G0BJ0Y3E2ZISaMbt68L4xe0MbugkdPMaN3KMv8Q4EJ0mnW9fmghzSYO/I/L9x6A8 niHT/X0N+fQsrKl4iXfHO0aX2KjTh+dd3D+gAN9MIIgYSg== X-Virus-Scanned: by MailRoute Received: from 013.lax.mailroute.net ([127.0.0.1]) by localhost (013.lax [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id uKCKq5Yfjfv6; Fri, 8 May 2026 16:11:28 +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 013.lax.mailroute.net (Postfix) with ESMTPSA id 4gBvHv0Z5Tzlfl5k; Fri, 8 May 2026 16:11:22 +0000 (UTC) Message-ID: Date: Fri, 8 May 2026 09:11:21 -0700 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: [RFC PATCH] scsi: scsi_transport_srp: Move long delayed work on system_dfl_long_wq To: Marco Crivellari , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Michal Hocko , "James E . J . Bottomley" , "Martin K . Petersen" References: <20260507143410.337267-1-marco.crivellari@suse.com> Content-Language: en-US From: Bart Van Assche In-Reply-To: <20260507143410.337267-1-marco.crivellari@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable On 5/7/26 7:34 AM, Marco Crivellari wrote: > Currently the code enqueue work items using {queue|mod}_delayed_work(), > using system_long_wq. This workqueue should be used when long works are > expected and it is a per-cpu workqueue. >=20 > The function(s) end up calling __queue_delayed_work(), which set a glob= al > timer that could fire anywhere, enqueuing the work where the timer fire= d. >=20 > Unbound works could benefit from scheduler task placement, to optimize > performance and power consumption. Long work shouldn't stick to a singl= e > CPU. >=20 > Recently, a new unbound workqueue specific for long running work has > been added: >=20 > =C2=A0=C2=A0=C2=A0=C2=A0c116737e972e ("workqueue: Add system_dfl_long_= wq for long unbound works") >=20 > Since the workqueue work doesn't rely on per-cpu variables, there is no > obvious reason that justify the use of a per-cpu workqueue. So change > system_long_wq with system_dfl_long_wq so that the work may benefit fro= m > scheduler task placement. This looks like unnecessary churn to me. The motivation for the introduction of system_dfl_long_wq seems very weak to me. Wouldn't we all be better off if commit c116737e972e would be reverted and if the behavior of system_long_wq would be modified from per-CPU into unbound? Thanks, Bart.