From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: KVM lock contention on 48 core AMD machine Date: Mon, 21 Mar 2011 21:48:19 +0300 Message-ID: <4D879D73.2090608@msgid.tls.msk.ru> References: <20110318123031.GB6066@8bytes.org> <4D871F6C.40207@redhat.com> <4D875842.9050308@redhat.com> <4D8773AA.8030408@redhat.com> <1300726498.2884.493.camel@edumazet-laptop> <4D8784A9.8040303@redhat.com> <1300727545.2884.513.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Avi Kivity , ben@iagu.net, KVM list To: Eric Dumazet Return-path: Received: from isrv.corpit.ru ([86.62.121.231]:36943 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753260Ab1CUSsW (ORCPT ); Mon, 21 Mar 2011 14:48:22 -0400 In-Reply-To: <1300727545.2884.513.camel@edumazet-laptop> Sender: kvm-owner@vger.kernel.org List-ID: 21.03.2011 20:12, Eric Dumazet wrote: > Le lundi 21 mars 2011 =C3=A0 19:02 +0200, Avi Kivity a =C3=A9crit : >=20 >> Any ideas on how to fix it? We could pre-allocate IDs and batch the= m in=20 >> per-cpu caches, but it seems like a lot of work. >> >=20 > Hmm, I dont know what syscalls kvm do, but even a timer_gettime() has= to > lock this idr_lock. I wonder why my testcase - 160 kvm guests on a 2-core AMD AthlonII CPU = - shows no contention of that sort, not at all... Yes sure, all these (linux) guests are idling at login: prompt, but I'd expect at least some gettimeofday() and some load average, -- everything stays close to zero. /mjt