From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10A4FC433DF for ; Mon, 25 May 2020 04:10:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E099B204EC for ; Mon, 25 May 2020 04:10:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="f90HLmxX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725969AbgEYEKK (ORCPT ); Mon, 25 May 2020 00:10:10 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:23116 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725849AbgEYEKK (ORCPT ); Mon, 25 May 2020 00:10:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590379808; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1KWB65Zd6HysINvlTNtvzqIZE9+EW9wQ3SY6GXwcmNY=; b=f90HLmxXL9Yzxt0RpRFSNHbf22a8h3tvTl/x+L+cCvXclxCfBz7/U01g4ZqwgUGFGh62SG DTIgz708bBj816+6ox/o7M/ZIgmxGVu8yLfKY6FCPgNEVh1XIMgk/4BBT+mSkqWD+B0a1l adVuJSC1yCXUIWZOnUkGmlv6OvP3ULs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-428-ozmA6KkgM_20Xt9D9-afjA-1; Mon, 25 May 2020 00:10:05 -0400 X-MC-Unique: ozmA6KkgM_20Xt9D9-afjA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 160801855A02; Mon, 25 May 2020 04:10:04 +0000 (UTC) Received: from T590 (ovpn-13-214.pek2.redhat.com [10.72.13.214]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5FB475D9DC; Mon, 25 May 2020 04:09:57 +0000 (UTC) Date: Mon, 25 May 2020 12:09:52 +0800 From: Ming Lei To: Bart Van Assche Cc: Christoph Hellwig , linux-block@vger.kernel.org, John Garry , Hannes Reinecke , Thomas Gleixner Subject: Re: blk-mq: improvement CPU hotplug (simplified version) v3 Message-ID: <20200525040952.GB791214@T590> References: <20200520170635.2094101-1-hch@lst.de> <0cbc37cf-5439-c68c-3581-b3c436932388@acm.org> <20200521025744.GC735749@T590> <9249e1cc-b6f2-010e-78d2-ead5a1b93464@acm.org> <20200521043305.GA741019@T590> <7accb5b2-6c7d-0e0d-56df-d06e8d9ac5af@acm.org> <20200522023923.GC755458@T590> <26169cd9-49b8-b949-aaa3-9745e821c86c@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <26169cd9-49b8-b949-aaa3-9745e821c86c@acm.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sat, May 23, 2020 at 08:19:58AM -0700, Bart Van Assche wrote: > On 2020-05-21 19:39, Ming Lei wrote: > > You may argue that two hw queue may share single managed interrupt, that > > is possible if driver plays the trick. But if driver plays the trick in > > this way, it is driver's responsibility to guarantee that the managed > > irq won't be shutdown if either of the two hctxs are active, such as, > > making sure that hctx->cpumask + hctx->cpumask <= this managed interrupt's affinity. > > It is definitely one strange enough case, and this patch doesn't > > suppose to cover this strange case. But, this patch won't break this > > case. Also just be curious, do you have such in-tree case? and are you > > sure the driver uses managed interrupt? > > I'm concerned about the block drivers that use RDMA (NVMeOF, SRP, iSER, > ...). The functions that accept an interrupt vector argument > (comp_vector), namely ib_alloc_cq() and ib_create_cq(), can be used in PCI_IRQ_AFFINITY isn't used in RDMA driver, so RDMA NIC uses non-managed irq. > such a way that completion interrupts are handled on another CPU than > those in hctx->cpumask. As I explained, this patchset doesn't rely on that interrupts have to be fired on hctx->cpumask, and it only changes the submission io path, which is blk-mq's generic code path which doesn't depend on any driver's specific behavior. Please let us know if your concerns are addressed. Thanks, Ming