From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH 3/6] perf record: add time-of-day option Date: Tue, 01 Mar 2011 15:35:36 -0700 Message-ID: <4D6D74B8.4010607@cisco.com> References: <1298865151-23656-1-git-send-email-daahern@cisco.com> <1298865151-23656-4-git-send-email-daahern@cisco.com> <1298989751.5226.863.camel@laptop> <4D6D0438.2090901@cisco.com> <1298993714.5226.871.camel@laptop> <4D6D13C6.5020807@cisco.com> <1298995250.5226.882.camel@laptop> <4D6D1A4C.1090009@cisco.com> <1298997435.5226.890.camel@laptop> <4D6D22A7.6000000@cisco.com> <1299018489.5226.940.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from sj-iport-3.cisco.com ([171.71.176.72]:4017 "EHLO sj-iport-3.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756526Ab1CAWfV (ORCPT ); Tue, 1 Mar 2011 17:35:21 -0500 In-Reply-To: <1299018489.5226.940.camel@laptop> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, acme@ghostprotocols.net, mingo@elte.hu, fweisbec@gmail.com, paulus@samba.org, tglx@linutronix.de On 03/01/2011 03:28 PM, Peter Zijlstra wrote: >> And for some silly reason I sense a time trap here (pun intended) ..... >> >> So your pushback is: >> 1. throw out the realtime-clock event patch, > > Well, no, you need continues samples to keep in sync, so having this is > required [*]. > >> 2. add a new CLOCK_TRACING type to clock_gettime with VDSO hook, > > Right, that is something we need anyway at some point in time. > >> 3. and use a synthesized event from userspace for snapshotting >> perf_clock to time-of-day -- similar to what I have now, but one that >> will guarantee a time-of-day to perf_clock correlation (versus the >> current one which hopes that perf_clock is the monotonic clock). > > I guess you could do that if we have full userspace tracing support, but > it wouldn't need synthesized events, it would need a pure userspace > event stream. I still don't see how this solves the need to trigger the initial sample into the event stream. David > > Thing is, I really dislike the ioctl() trigger > > >