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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 3B95CC433E9 for ; Tue, 9 Feb 2021 16:16:39 +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 6EA9C64EB8 for ; Tue, 9 Feb 2021 16:16:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6EA9C64EB8 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]:45348 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9Vgr-00043i-Bp for qemu-devel@archiver.kernel.org; Tue, 09 Feb 2021 11:16:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49642) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9VeG-0001vM-Ut for qemu-devel@nongnu.org; Tue, 09 Feb 2021 11:13:56 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:59322) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9VeE-0006z0-JF for qemu-devel@nongnu.org; Tue, 09 Feb 2021 11:13:56 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612887233; h=from:from:reply-to: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=LuisdI+PPEnAlDv2vwvrweoiB88cL497k0m9hlhWf1E=; b=hDloWH3pUj3WugJHaiCPexONLeAvReU9Y8lH72w/1Hw6RDaABWe81iwhNnp59UTbBLmX/R BcVFtA9slVTuwTB0MMUW6mTvzLS5COtiXgwdNn+qoQFHTu2VNFcCuNukO1+a0eoC3pudu3 kq9R5ncE3iZw+AwS8qIoCmOGapLtYAM= 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-jaDg_at7NEuiQWM8cuq1OQ-1; Tue, 09 Feb 2021 11:13:52 -0500 X-MC-Unique: jaDg_at7NEuiQWM8cuq1OQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 017AB1020C20; Tue, 9 Feb 2021 16:13:51 +0000 (UTC) Received: from redhat.com (ovpn-115-66.ams2.redhat.com [10.36.115.66]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7EF5119C78; Tue, 9 Feb 2021 16:13:47 +0000 (UTC) Date: Tue, 9 Feb 2021 16:13:43 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Subject: Re: [PATCH v3 1/2] qemu-nbd: Use SOMAXCONN for socket listen() backlog Message-ID: <20210209161343.GT1166421@redhat.com> References: <20210209152759.209074-1-eblake@redhat.com> <20210209152759.209074-2-eblake@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210209152759.209074-2-eblake@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.57, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Kevin Wolf , qemu-block@nongnu.org, rjones@redhat.com, qemu-stable@nongnu.org, qemu-devel@nongnu.org, nsoffer@redhat.com, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Feb 09, 2021 at 09:27:58AM -0600, Eric Blake wrote: > Our default of a backlog of 1 connection is rather puny; it gets in > the way when we are explicitly allowing multiple clients (such as > qemu-nbd -e N [--shared], or nbd-server-start with its default > "max-connections":0 for unlimited), but is even a problem when we > stick to qemu-nbd's default of only 1 active client but use -t > [--persistent] where a second client can start using the server once > the first finishes. While the effects are less noticeable on TCP > sockets (since the client can poll() to learn when the server is ready > again), it is definitely observable on Unix sockets, where on Unix, a > client will fail with EAGAIN and no recourse but to sleep an arbitrary > amount of time before retrying if the server backlog is already full. > > Since QMP nbd-server-start is always persistent, it now always > requests a backlog of SOMAXCONN; meanwhile, qemu-nbd will request > SOMAXCONN if persistent, otherwise its backlog should be based on the > expected number of clients. > > See https://bugzilla.redhat.com/1925045 for a demonstration of where > our low backlog prevents libnbd from connecting as many parallel > clients as it wants. > > Reported-by: Richard W.M. Jones > Signed-off-by: Eric Blake > CC: qemu-stable@nongnu.org > --- > blockdev-nbd.c | 7 ++++++- > qemu-nbd.c | 10 +++++++++- > 2 files changed, 15 insertions(+), 2 deletions(-) Reviewed-by: Daniel P. Berrangé Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|