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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 4478FC433DF for ; Thu, 28 May 2020 08:51:48 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0BBB32088E for ; Thu, 28 May 2020 08:51:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OPAFaA2C" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BBB32088E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52544 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jeEGR-0004No-6d for qemu-devel@archiver.kernel.org; Thu, 28 May 2020 04:51:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59790) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jeEFj-00035h-JU for qemu-devel@nongnu.org; Thu, 28 May 2020 04:51:03 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:55784 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jeEFh-0002i5-OA for qemu-devel@nongnu.org; Thu, 28 May 2020 04:51:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590655860; 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=1C6BG9c/JaMiOIm41N7LYwcVaqkjDcuIb5Ie7fT48xw=; b=OPAFaA2CtRNiTl/YD1dsUtkJbw4hm8M4EHEZi13cs7PZ+i3S1XlOHvy06qxU3+uTJojrwp Z5Z8jLw1f/uKsqh5Eeisojohr6jY4qlqs+WnbUFixIb8Tzxx4n+RDpCvj3x4bPltjt+prz hQmV2o4O6Rbfma5WidY7VfZcRjEGrKI= 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-389-UU0POPhrMgO765xHNJN4vA-1; Thu, 28 May 2020 04:50:58 -0400 X-MC-Unique: UU0POPhrMgO765xHNJN4vA-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 7D586107ACCA; Thu, 28 May 2020 08:50:57 +0000 (UTC) Received: from localhost (ovpn-114-90.ams2.redhat.com [10.36.114.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2FB795D9EF; Thu, 28 May 2020 08:50:53 +0000 (UTC) Date: Thu, 28 May 2020 09:50:52 +0100 From: Stefan Hajnoczi To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH v4 3/5] virtio-scsi: default num_queues to -smp N Message-ID: <20200528085052.GA148227@stefanha-x1.localdomain> References: <20200527102925.128013-1-stefanha@redhat.com> <20200527102925.128013-4-stefanha@redhat.com> <20200527103817.GI2665520@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200527103817.GI2665520@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="NzB8fVQJ5HfG6fxh" Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=stefanha@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/28 03:11:04 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Pankaj Gupta , Eduardo Habkost , qemu-block@nongnu.org, "Michael S. Tsirkin" , cohuck@redhat.com, qemu-devel@nongnu.org, Max Reitz , Paolo Bonzini , Fam Zheng , Raphael Norwitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --NzB8fVQJ5HfG6fxh Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, May 27, 2020 at 11:38:17AM +0100, Daniel P. Berrang=E9 wrote: > On Wed, May 27, 2020 at 11:29:23AM +0100, Stefan Hajnoczi wrote: > > Automatically size the number of virtio-scsi-pci, vhost-scsi-pci, and > > vhost-user-scsi-pci request virtqueues to match the number of vCPUs. > > Other transports continue to default to 1 request virtqueue. >=20 > IIRC this was raised on earlier versions of the series, but i don't > recall the outcome and no caveats are mentioned here... >=20 > Is this default still valid for very large $vCPUs. eg if I run QEMU > with "-smp 512" or even larger (I've seen people discussing 1000's of > CPUs), is this going to cause problems with the virtio-scsi default > queue counts ? Is there such a thing as "too large" for the num > of queues setting ? num vectors defaults to a value derived from > num queues, so is there concept of "too large" for num of vectors > setting ? >=20 > Ideally the commit message would answer these questions for future > reference. Same for the next patch to virtio-blk Good point. Actually this patch and the virtio-blk ones no longer contain the queue number policy. The new virtio_pci_optimal_num_queues() function encapsulates the policy to avoid duplication. I'll resend and update that patch with the full rationale. Thanks! --NzB8fVQJ5HfG6fxh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAl7Pe2wACgkQnKSrs4Gr c8gjewf7BFjphWoBtrZIEwZIUOEaV0uAPweq3FBBkF8RyL2CuIbJvefAMqidt3xC /Y4edJpqoItQcw+6wocsZtu0dsA39ZD2fi7wDIKluRPI84fY2MzidlKQ51dDNOxH DQvtKdA3BFNMFN5VvoCC5RO2KRDCW9kCwBlektSJ785MgxDuD3oK+TgGwwW8gV1G ZcfaSFkZ0hzZ7JoVDh4wJuZL5MkqOpXBh8U/aXZpO7pDt998WcnV+1zqdHVOYn+3 M6AC1r666PoYFckAVb1qMCKV9tQK9Z7Wg05LoQim1OT7aQ3pih3RGRoOYdfg14jn /CEptjyYM/ohjf0p5F5FCMHBux0XLQ== =3y6w -----END PGP SIGNATURE----- --NzB8fVQJ5HfG6fxh--