From owner-svn-src-head@freebsd.org Thu Jun 2 11:28:07 2016 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 11904B64D5B; Thu, 2 Jun 2016 11:28:07 +0000 (UTC) (envelope-from royger@gmail.com) Received: from mail-wm0-x22b.google.com (mail-wm0-x22b.google.com [IPv6:2a00:1450:400c:c09::22b]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 9C9121A1E; Thu, 2 Jun 2016 11:28:06 +0000 (UTC) (envelope-from royger@gmail.com) Received: by mail-wm0-x22b.google.com with SMTP id a136so225291055wme.0; Thu, 02 Jun 2016 04:28:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=JVeaj5ZH4eEAnT5ngbHOBS5k/8E8op0Z+mxESMj9wgI=; b=B4M+v5FrJdVvTeIF73PI1SOgTozvcrlRBVzdqiUN3HN9uUhhmS2gX+yB5WymhkUbRc QhYxTRWQeqrfi/AD/97Cbg9FGpFcPcpFntJKr+khgRdJwn46Tron+/DjqHXwicvG4PZJ VClQfjWA/4e1EdZSdSSwThvuzAbUjvG0IdA+xzbK/sLNlnQFMsyeWnwbYFxpEkdrbzaA iLDIZS/BKEG2hgENZTV/GGvWMvhX2avtW08sKjiMagYqUtD5p06A6bkKWiHFe41WgZ6v 6kuJQV53ayj2zw5KCWTdXpfrmc7OjshkKVzRZNA403E1BhpK26YK7drDi2HVc8QoCw6X ttZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:date:from:to:subject:message-id :references:mime-version:content-disposition :content-transfer-encoding:in-reply-to:user-agent; bh=JVeaj5ZH4eEAnT5ngbHOBS5k/8E8op0Z+mxESMj9wgI=; b=Slv1MzzaCMsIUl/SOyR1yEThuB4t1MUYTKETXaFaK+LU2KovVoDsywukaDC1Hm+Qpe DafzjHiYW9zrJ3AnDSc8pD7P+q+XTsGxHl9rOBSmETzA4sJHBMeIAN3AL338kQyQ5vyG qCdJRB9wgr8beTb1LHAZD5GIEfG41GRgEjaydm6PbN806ZjdhSbmtctZ2Jmvj9AXB73E ud6HRcArVhZkySN5+NeNWEuhua+mVbBTXugkrUP+UJbRWEOVwKyyyIqD1GkVt95H0Z86 GxF0CXCNkxQKdwauenQIjlAQwvXqvjWX0igLYPHPhaUQU8ZIIF0CYS4PMuO5OMGiArWl ySvg== X-Gm-Message-State: ALyK8tJ7WRe4kGwEctuh4KaRRoKbCUImyKyxVjionwYIwRqzu2wvbkN0BFk85K0W1YF/Kg== X-Received: by 10.194.175.36 with SMTP id bx4mr8119107wjc.35.1464866885169; Thu, 02 Jun 2016 04:28:05 -0700 (PDT) Received: from localhost (98.red-79-145-83.dynamicip.rima-tde.net. [79.145.83.98]) by smtp.gmail.com with ESMTPSA id d86sm39798726wmh.4.2016.06.02.04.28.03 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 02 Jun 2016 04:28:04 -0700 (PDT) Sender: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= Date: Thu, 2 Jun 2016 13:28:01 +0200 From: Roger Pau =?iso-8859-1?Q?Monn=E9?= To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r301197 - head/sys/dev/xen/netfront Message-ID: <20160602112801.yqxgblpmxml6d3uz@mac> References: <201606021114.u52BEQqB047172@repo.freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <201606021114.u52BEQqB047172@repo.freebsd.org> User-Agent: Mutt/1.6.0-neo (2016-04-07) X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Jun 2016 11:28:07 -0000 On Thu, Jun 02, 2016 at 11:14:26AM +0000, Roger Pau Monné wrote: > Author: royger > Date: Thu Jun 2 11:14:26 2016 > New Revision: 301197 > URL: https://svnweb.freebsd.org/changeset/base/301197 > > Log: > xen-netfront: always keep the Rx ring full of requests > > This is based on Linux commit 1f3c2eba1e2d866ef99bb9b10ade4096e3d7607c from > David Vrabel: > > A full Rx ring only requires 1 MiB of memory. This is not enough memory > that it is useful to dynamically scale the number of Rx requests in the ring > based on traffic rates, because: > > a) Even the full 1 MiB is a tiny fraction of a typically modern Linux > VM (for example, the AWS micro instance still has 1 GiB of memory). > > b) Netfront would have used up to 1 MiB already even with moderate > data rates (there was no adjustment of target based on memory > pressure). > > c) Small VMs are going to typically have one VCPU and hence only one > queue. > > Keeping the ring full of Rx requests handles bursty traffic better than > trying to converge on an optimal number of requests to keep filled. > > Reviewed by: Wei Liu > Sponsored by: Citrix Systems R&D Differential revision: https://reviews.freebsd.org/D6610