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=-15.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 092BBC433E0 for ; Tue, 9 Feb 2021 16:14:33 +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 9933B64E99 for ; Tue, 9 Feb 2021 16:14:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9933B64E99 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]:41918 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9Vep-00025b-Jo for qemu-devel@archiver.kernel.org; Tue, 09 Feb 2021 11:14:31 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49284) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9Vcw-0000Rv-04 for qemu-devel@nongnu.org; Tue, 09 Feb 2021 11:12:34 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:54488) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9Vct-0006Pu-2R for qemu-devel@nongnu.org; Tue, 09 Feb 2021 11:12:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612887150; 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=gl8LCDm44x9Y0C5OIt1reKyHwfmhQWB2XzQqpetO8X0=; b=OrkJBXQJecVtjWYS9nMbAR8Kd5pZmyaFXwrba704fnVMg+SuLlBkuTk/y11eLApFb/kg36 BAXUvsOKewFNYnHMMofudMxMDnmZELqJvQudVYh4fOpwolljvlS/M6B377ZGDlAqraBNta MciPqkcO4KP+5kwlhRDIPbuD64/bHCc= 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-548-V6LETS3aOB-HsWjxPUsTgw-1; Tue, 09 Feb 2021 11:12:25 -0500 X-MC-Unique: V6LETS3aOB-HsWjxPUsTgw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 03213803F4A; Tue, 9 Feb 2021 16:12:24 +0000 (UTC) Received: from [10.3.114.150] (ovpn-114-150.phx2.redhat.com [10.3.114.150]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 606B5101E679; Tue, 9 Feb 2021 16:12:23 +0000 (UTC) Subject: Re: [PATCH v3 1/2] qemu-nbd: Use SOMAXCONN for socket listen() backlog To: "Richard W.M. Jones" References: <20210209152759.209074-1-eblake@redhat.com> <20210209152759.209074-2-eblake@redhat.com> <20210209160851.GA30079@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Tue, 9 Feb 2021 10:12:22 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210209160851.GA30079@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 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, NICE_REPLY_A=-0.265, 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=ham 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: , Cc: Kevin Wolf , berrange@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, qemu-stable@nongnu.org, nsoffer@redhat.com, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/9/21 10:08 AM, Richard W.M. Jones wrote: > 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 s/where on Unix/where on Linux/ >> 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(-) >> > > Works fine here, so: > > Tested-by: Richard W.M. Jones > Thanks for testing. > Rich. > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org