Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758603AbZJHPcJ (ORCPT ); Thu, 8 Oct 2009 11:32:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758569AbZJHPcI (ORCPT ); Thu, 8 Oct 2009 11:32:08 -0400 Received: from hera.kernel.org ([140.211.167.34]:32933 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758498AbZJHPcG (ORCPT ); Thu, 8 Oct 2009 11:32:06 -0400 Date: Thu, 8 Oct 2009 15:30:52 GMT From: tip-bot for Arjan van de Ven Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, torvalds@linux-foundation.org, arjan@linux.intel.com, efault@gmx.de, peterz@infradead.org, elendil@planet.nl, arjan@infradead.org, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, arjan@linux.intel.com, torvalds@linux-foundation.org, elendil@planet.nl, peterz@infradead.org, efault@gmx.de, arjan@infradead.org, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <20091008064041.67219b13@infradead.org> References: <20091008064041.67219b13@infradead.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/urgent] x86, timers: Check for pending timers after (device) interrupts Message-ID: Git-Commit-ID: 9bcbdd9c58617f1301dd4f17c738bb9bc73aca70 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Thu, 08 Oct 2009 15:30:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2953 Lines: 81 Commit-ID: 9bcbdd9c58617f1301dd4f17c738bb9bc73aca70 Gitweb: http://git.kernel.org/tip/9bcbdd9c58617f1301dd4f17c738bb9bc73aca70 Author: Arjan van de Ven AuthorDate: Thu, 8 Oct 2009 06:40:41 -0700 Committer: Ingo Molnar CommitDate: Thu, 8 Oct 2009 17:27:27 +0200 x86, timers: Check for pending timers after (device) interrupts Now that range timers and deferred timers are common, I found a problem with these using the "perf timechart" tool. Frans Pop also reported high scheduler latencies via LatencyTop, when using iwlagn. It turns out that on x86, these two 'opportunistic' timers only get checked when another "real" timer happens. These opportunistic timers have the objective to save power by hitchhiking on other wakeups, as to avoid CPU wakeups by themselves as much as possible. The change in this patch runs this check not only at timer interrupts, but at all (device) interrupts. The effect is that: 1) the deferred timers/range timers get delayed less 2) the range timers cause less wakeups by themselves because the percentage of hitchhiking on existing wakeup events goes up. I've verified the working of the patch using "perf timechart", the original exposed bug is gone with this patch. Frans also reported success - the latencies are now down in the expected ~10 msec range. Signed-off-by: Arjan van de Ven Tested-by: Frans Pop Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Mike Galbraith LKML-Reference: <20091008064041.67219b13@infradead.org> Signed-off-by: Ingo Molnar --- arch/x86/kernel/irq.c | 2 ++ arch/x86/kernel/smp.c | 1 + 2 files changed, 3 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 74656d1..3912061 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -244,6 +244,7 @@ unsigned int __irq_entry do_IRQ(struct pt_regs *regs) __func__, smp_processor_id(), vector, irq); } + run_local_timers(); irq_exit(); set_irq_regs(old_regs); @@ -268,6 +269,7 @@ void smp_generic_interrupt(struct pt_regs *regs) if (generic_interrupt_extension) generic_interrupt_extension(); + run_local_timers(); irq_exit(); set_irq_regs(old_regs); diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index ec1de97..d915d95 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -198,6 +198,7 @@ void smp_reschedule_interrupt(struct pt_regs *regs) { ack_APIC_irq(); inc_irq_stat(irq_resched_count); + run_local_timers(); /* * KVM uses this interrupt to force a cpu out of guest mode */ -- 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/