From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 3/3] KVM: MMU: Separate trivial NULL check out from rmap_get_next() Date: Tue, 20 Mar 2012 13:56:59 +0200 Message-ID: <4F68708B.8080507@redhat.com> References: <20120315181856.2ced0a28.yoshikawa.takuya@oss.ntt.co.jp> <20120315182127.07600c50.yoshikawa.takuya@oss.ntt.co.jp> <4F61BB1D.6050209@redhat.com> <20120315191553.32d6fc36.yoshikawa.takuya@oss.ntt.co.jp> <4F61DA07.4010200@redhat.com> <20120315224142.67713f557239116a99cd18af@gmail.com> <4F61F2B7.1020202@redhat.com> <20120320153713.a952558c3a3d84a686665261@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Takuya Yoshikawa , mtosatti@redhat.com, kvm@vger.kernel.org To: Takuya Yoshikawa Return-path: Received: from mx1.redhat.com ([209.132.183.28]:35231 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759770Ab2CTL5G (ORCPT ); Tue, 20 Mar 2012 07:57:06 -0400 In-Reply-To: <20120320153713.a952558c3a3d84a686665261@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/20/2012 08:37 AM, Takuya Yoshikawa wrote: > On Thu, 15 Mar 2012 15:46:31 +0200 > Avi Kivity wrote: > > > You can look at what's happening by doing > > > > perf record -a -f > > perf report > > > > using the TUI, select 'annotate rmap_get_next' > > > > You should see where the time is spent. > > > > Since the default sampling rate was not enough to get consistent numbers, > I raised the frequency to 50K/sec; so there was surely some overheads > during that sampling. > > From the result below, it seems to be the prologue and epilogue on which > we spent most of our time. > > I can only assume that the cpu is processing these instructions perfectly and each is taking 1 cycle (or less). I don't see how else we can arrive at such results. -- error compiling committee.c: too many arguments to function