From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: Performance issue Date: Thu, 29 Nov 2012 15:56:10 +0200 Message-ID: <20121129135610.GB17318@redhat.com> References: <201211281339.17589.vrozenfe@redhat.com> <201211291356.21344.vrozenfe@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Vadim Rozenfeld , kvm@vger.kernel.org To: George-Cristian =?utf-8?Q?B=C3=AErzan?= Return-path: Received: from mx1.redhat.com ([209.132.183.28]:19338 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752681Ab2K2OMW convert rfc822-to-8bit (ORCPT ); Thu, 29 Nov 2012 09:12:22 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Nov 29, 2012 at 03:45:52PM +0200, George-Cristian B=C3=AErzan w= rote: > On Thu, Nov 29, 2012 at 1:56 PM, Vadim Rozenfeld wrote: > >> I've also added +hv_relaxed since then, but this is the command I'= m > > > > I would suggest activating relaxed timing for all W2K8R2/Win7 guest= s. >=20 > Is there any place I can read up on the downsides of this for Linux, > or is Just Better? >=20 You shouldn't use hyper-v flags for Linux guests. In theory Linux shoul= d just ignore them, in practice there may be bugs that will prevent Linux from detecting that it runs as a guest and disable optimizations. > >>>> Other than that, was looking into a profiling trace of the softw= are > >> running and a lot of time (60%?) is spent calling two functions fr= om > >> hal.dll, HalpGetPmTimerSleepModePerfCounter when I disable HPET, a= nd > >> HalpHPETProgramRolloverTimer which do point at something related t= o > >> the timers. > >> > > It means that hyper-v time stamp source was not activated. >=20 > I recompiled the whole kernel, with your patch, and while I cannot > check at 70Mbps now, a test stream of 20 seems to do better. Also, no= w > I don't see any of those functions, which used to account ~60% of the > time spent by the program. I'm waiting for the customer to come back > and start the 'real' stream, but from my tests, time spent in hal.dll > is now an order of magnitude smaller. >=20 > -- > George-Cristian B=C3=AErzan -- Gleb.