From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753348AbXDBHGh (ORCPT ); Mon, 2 Apr 2007 03:06:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753325AbXDBHGh (ORCPT ); Mon, 2 Apr 2007 03:06:37 -0400 Received: from gw.goop.org ([64.81.55.164]:57755 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753348AbXDBHGg (ORCPT ); Mon, 2 Apr 2007 03:06:36 -0400 Message-ID: <4610AB6E.8020209@goop.org> Date: Mon, 02 Apr 2007 00:06:22 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 1.5.0.10 (X11/20070302) MIME-Version: 1.0 To: Andi Kleen CC: Andrew Morton , virtualization@lists.osdl.org, lkml , Zachary Amsden , Dan Hecht , john stultz Subject: Re: [patch 17/17] Add a sched_clock paravirt_op References: <20070402055652.610711908@goop.org> <200704020809.42373.ak@suse.de> <4610A70A.7010105@goop.org> <200704020850.32274.ak@suse.de> In-Reply-To: <200704020850.32274.ak@suse.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen wrote: > Do you also get a clock for stolen nanoseconds? > What you actually get is how many ns the CPU spent in each state. Stolen is runnable+offline. > No need for cycles, you could just subtract the stolen ns if you > can get those. It just seems like a simpler interface to just allow overriding sched_clock, rather than exposing sched_clock's internals and fiddling with those. There's really nothing in the existing sched_clock which can be profitably reused in the Xen case. VMI can make use of the cycles_2_ns conversion, which is why I made it available for its use. To be specific, this is the whole Xen sched_clock function: /* Xen sched_clock implementation. Returns the number of RUNNING ns */ unsigned long long xen_sched_clock(void) { struct vcpu_runstate_info state; cycle_t now; unsigned long long ret; preempt_disable(); now = xen_clocksource_read(); get_runstate_snapshot(&state); WARN_ON(state.state != RUNSTATE_running); ret = state.time[RUNSTATE_running] + (now - state.state_entry_time); preempt_enable(); return ret; } J