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=-7.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 62845CA9EB7 for ; Mon, 21 Oct 2019 12:53:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 388B72089C for ; Mon, 21 Oct 2019 12:53:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Duf//l38" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726767AbfJUMxq (ORCPT ); Mon, 21 Oct 2019 08:53:46 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:33837 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727256AbfJUMxq (ORCPT ); Mon, 21 Oct 2019 08:53:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571662424; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Z1ne9nHEe0n21mZZ0VzO+ppilu0NzYXp+z/uDCmekFQ=; b=Duf//l38jLZt0UItFD7LS8ZPIvGXZads/8GYya73owK0NFIW4dY5oDqIPO0NZE8ldeheR+ AfIcxHFXR+4PJYWTA5LFs3u/qY6Ych+BEt0AK+mV88NFgR2vv4R60nCG0r5BphXPSLYXJU /qA7a+uXScsfPKnJDU+YB1dAhL3ISfE= 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-64-DYAcTfNCPlaZxS3VyE-9zQ-1; Mon, 21 Oct 2019 08:53:43 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 61F5E1800E00; Mon, 21 Oct 2019 12:53:41 +0000 (UTC) Received: from ming.t460p (ovpn-8-16.pek2.redhat.com [10.72.8.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DD81460BE2; Mon, 21 Oct 2019 12:53:33 +0000 (UTC) Date: Mon, 21 Oct 2019 20:53:28 +0800 From: Ming Lei To: John Garry Cc: Jens Axboe , linux-block@vger.kernel.org, Bart Van Assche , Hannes Reinecke , Christoph Hellwig , Thomas Gleixner , Keith Busch Subject: Re: [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug Message-ID: <20191021125327.GA25864@ming.t460p> References: <20191016120729.GB5515@ming.t460p> <9dbc14ab-65cd-f7ac-384c-2dbe03575ee7@huawei.com> <55a84ea3-647d-0a76-596c-c6c6b2fc1b75@huawei.com> <20191020101404.GA5103@ming.t460p> <10aac76a-26bb-bcda-c6ea-b39ca66d6740@huawei.com> <20191021093448.GA22635@ming.t460p> <9e6e86a5-7247-4648-9df9-61f81d2df413@huawei.com> <20191021102401.GB22635@ming.t460p> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: DYAcTfNCPlaZxS3VyE-9zQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Oct 21, 2019 at 12:49:53PM +0100, John Garry wrote: > > > >=20 > > >=20 > > > Yes, we share tags among all queues, but we generate the tag - known = as IPTT > > > - in the LLDD now, as we can no longer use the request tag (as it is = not > > > unique per all queues): > > >=20 > > > https://github.com/hisilicon/kernel-dev/commit/087b95af374be6965583c1= 673032fb33bc8127e8#diff-f5d8fff19bc539a7387af5230d4e5771R188 > > >=20 > > > As I said, the branch is messy and I did have to fix 087b95af374. > >=20 > > Firstly this way may waste lots of memory, especially the queue depth i= s > > big, such as, hisilicon V3's queue depth is 4096. > >=20 > > Secondly, you have to deal with queue busy efficiently and correctly, > > for example, your real hw tags(IPTT) can be used up easily, and how > > will you handle these dispatched request? >=20 > I have not seen scenario of exhausted IPTT. And IPTT count is same as SCS= I > host.can_queue, so SCSI midlayer should ensure that this does not occur. That check isn't correct, and each hw queue should have allowed .can_queue in-flight requests. >=20 > >=20 > > Finally, you have to evaluate the performance effect, this is highly > > related with how to deal with out-of-IPTT. >=20 > Some figures from our previous testing: >=20 > Managed interrupt without exposing multiple queues: 3M IOPs > Managed interrupt with exposing multiple queues: 2.6M IOPs Then you see the performance regression. Thanks, Ming