From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49807) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V7SBB-00042l-Im for qemu-devel@nongnu.org; Thu, 08 Aug 2013 11:31:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V7SB2-000794-DU for qemu-devel@nongnu.org; Thu, 08 Aug 2013 11:31:09 -0400 Received: from mail-ea0-x232.google.com ([2a00:1450:4013:c01::232]:56426) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V7SB2-00078h-5l for qemu-devel@nongnu.org; Thu, 08 Aug 2013 11:31:00 -0400 Received: by mail-ea0-f178.google.com with SMTP id a15so1484679eae.23 for ; Thu, 08 Aug 2013 08:30:59 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <5203B991.90405@redhat.com> Date: Thu, 08 Aug 2013 17:30:25 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1375972194-3090-1-git-send-email-benoit@irqsave.net> <1375972194-3090-4-git-send-email-benoit@irqsave.net> In-Reply-To: <1375972194-3090-4-git-send-email-benoit@irqsave.net> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH V4 3/5] block: Enable the new throttling code in the block layer. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?ISO-8859-15?Q?Beno=EEt_Canet?= Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com Il 08/08/2013 16:29, Benoît Canet ha scritto: > tip: Do not ever use the cfg scheduler in the guest with this code. > It gives incorrect throttling. This is not really accurate; the cfq scheduler reorders reads and writes to have longer bursts, and these sometimes exceed the rate you set. I understood this is mostly for separate rd/wr settings, or did you reproduce it with "total" rates too? Also, it would be better to have a workaround for this. Perhaps we could simply make the default value of max nonzero? In the old throttling code the slice time is 0.1s, so perhaps we could see what happens with max=0.1*avg. Paolo