Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758070Ab3EGMDU (ORCPT ); Tue, 7 May 2013 08:03:20 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:28122 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757621Ab3EGMDT (ORCPT ); Tue, 7 May 2013 08:03:19 -0400 X-IronPort-AV: E=Sophos;i="4.87,628,1363132800"; d="scan'208";a="22584554" Date: Tue, 7 May 2013 12:58:32 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Ian Campbell CC: Stefano Stabellini , "xen-devel@lists.xensource.com" , "marc.zyngier@arm.com" , "konrad.wilk@oracle.com" , "will.deacon@arm.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [Xen-devel] [PATCH RFC v2 4/4] xen/arm: account for stolen ticks In-Reply-To: <1367918270.26321.39.camel@zakaz.uk.xensource.com> Message-ID: References: <1367851878-21629-4-git-send-email-stefano.stabellini@eu.citrix.com> <1367918270.26321.39.camel@zakaz.uk.xensource.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3144 Lines: 94 On Tue, 7 May 2013, Ian Campbell wrote: > On Mon, 2013-05-06 at 15:51 +0100, Stefano Stabellini wrote: > > Register the runstate_memory_area with the hypervisor. > > Use pv_time_ops.steal_clock to account for stolen ticks. > > > > Signed-off-by: Stefano Stabellini > > --- > > arch/arm/xen/enlighten.c | 23 +++++++++++++++++++++++ > > 1 files changed, 23 insertions(+), 0 deletions(-) > > > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c > > index ee86bfa..2a5cc82 100644 > > --- a/arch/arm/xen/enlighten.c > > +++ b/arch/arm/xen/enlighten.c > > @@ -14,7 +14,10 @@ > > #include > > #include > > #include > > +#include > > #include > > +#include > > +#include > > #include > > #include > > #include > > @@ -152,6 +155,20 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma, > > } > > EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range); > > > > +unsigned long long xen_stolen_accounting(int cpu) > > +{ > > + struct vcpu_runstate_info state; > > + > > + if (cpu != get_cpu()) > > get_cpu disables preempt, so you need a matching put_cpu. Oops, thanks. > But actually I think you just want smp_processor_id and you probably > want the BUG_ON form to get unlikely etc. > > That said, you don't use cpu for anything else, so why not drop it > entirely? Ah, that's right, legacy of the past. I'll do that. > > + BUG(); > > + > > + xen_get_runstate_snapshot(&state); > > + > > + WARN_ON(state.state != RUNSTATE_running); > > + > > + return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline]; > > +} > > + > > static void __init xen_percpu_init(void *unused) > > { > > struct vcpu_register_vcpu_info info; > > @@ -170,6 +187,8 @@ static void __init xen_percpu_init(void *unused) > > BUG(); > > per_cpu(xen_vcpu, cpu) = vcpup; > > > > + xen_setup_runstate_info(cpu); > > + > > enable_percpu_irq(xen_events_irq, 0); > > } > > > > @@ -301,6 +320,10 @@ static int __init xen_init_events(void) > > > > on_each_cpu(xen_percpu_init, NULL, 0); > > > > + pv_time_ops.steal_clock = xen_stolen_accounting; > > + static_key_slow_inc(¶virt_steal_enabled); > > + static_key_slow_inc(¶virt_steal_rq_enabled); > > We don't seem to do this on x86 -- is that a bug on x86 on Xen? On x86 we do all the accounting in do_stolen_accounting, called from our own interrupt handler (xen_timer_interrupt). I don't think we would gain anything by using the common infrastructure, we would actually loose the idle ticks accounting we do there. Speaking of which, I don't think that pv_time_ops.steal_clock would properly increase CPUTIME_IDLE the way we do in do_stolen_accounting. How much of an issue is that? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/