From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:40766) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QzlzX-0002aE-JP for qemu-devel@nongnu.org; Sat, 03 Sep 2011 04:54:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QzlzW-0004vM-H4 for qemu-devel@nongnu.org; Sat, 03 Sep 2011 04:54:19 -0400 Received: from mail-qw0-f43.google.com ([209.85.216.43]:47180) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QzlzW-0004vG-D8 for qemu-devel@nongnu.org; Sat, 03 Sep 2011 04:54:18 -0400 Received: by qwm42 with SMTP id 42so2561406qwm.30 for ; Sat, 03 Sep 2011 01:54:17 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <4E5DF31A.1@redhat.com> From: Blue Swirl Date: Sat, 3 Sep 2011 08:53:57 +0000 Message-ID: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH, RFC] trace: implement guest tracepoint passthrough List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dhaval Giani Cc: qemu-devel , =?UTF-8?B?TGx1w61z?= , Avi Kivity , Stefan Hajnoczi On Wed, Aug 31, 2011 at 6:00 PM, Dhaval Giani wrot= e: > On Wed, Aug 31, 2011 at 10:58 AM, Blue Swirl wrote= : >> On Wed, Aug 31, 2011 at 8:38 AM, Avi Kivity wrote: >>> On 08/26/2011 10:06 PM, Blue Swirl wrote: >>>> >>>> Let guests inject tracepoint data via fw_cfg device. >>>> >>>> >>> >>> At least on x86, fw_cfg is pretty slow, involving multiple exits. =C2= =A0IMO, for >>> kvm, even one exit per tracepoint is too high. =C2=A0We need to use a s= hared >>> memory transport with a way to order guest/host events later on (by usi= ng a >>> clock). >> >> This could be an easy way, if the guest always had access to an >> accurate clock, but that may not be the case. >> > > From what I understand, kvmclock should be good enoguh for this > purpose. That is what I am using. It's only available for KVM on x86, that is most certainly not enough.