Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756260Ab0BJSfk (ORCPT ); Wed, 10 Feb 2010 13:35:40 -0500 Received: from mga01.intel.com ([192.55.52.88]:26656 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755080Ab0BJSfg (ORCPT ); Wed, 10 Feb 2010 13:35:36 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.49,445,1262592000"; d="scan'208";a="539597329" Date: Wed, 10 Feb 2010 10:35:31 -0800 From: "Pallipadi, Venkatesh" To: lenb@kernel.org Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, alex.shi@intel.com, ming.m.lin@intel.com Subject: [PATCH] acpi: Be in TS_POLLING state during mwait based C-state entry Message-ID: <20100210183530.GA5426@linux-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2416 Lines: 75 ACPI deep C-state entry had a long standing bug/missing feature, wherein we were sending resched IPIs when an idle CPU is in mwait based deep C-state. Only mwait based C1 was using the write to the monitored address to wake up mwait'ing CPU. This patch changes the code to retain TS_POLLING bit if we are entering an mwait based deep C-state. The patch has been verified to reduce the number of resched IPIs in general and also improves the performance/power on workloads with low system utilization (i.e., when mwait based deep C-states are being used). Reported-by: Lin Ming Tested-by: Alex Shi Signed-off-by: Venkatesh Pallipadi --- drivers/acpi/processor_idle.c | 28 ++++++++++++++++------------ 1 files changed, 16 insertions(+), 12 deletions(-) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 7c0441f..8abe91a 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -872,12 +872,14 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, return(acpi_idle_enter_c1(dev, state)); local_irq_disable(); - current_thread_info()->status &= ~TS_POLLING; - /* - * TS_POLLING-cleared state must be visible before we test - * NEED_RESCHED: - */ - smp_mb(); + if (cx->entry_method != ACPI_CSTATE_FFH) { + current_thread_info()->status &= ~TS_POLLING; + /* + * TS_POLLING-cleared state must be visible before we test + * NEED_RESCHED: + */ + smp_mb(); + } if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING; @@ -957,12 +959,14 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, } local_irq_disable(); - current_thread_info()->status &= ~TS_POLLING; - /* - * TS_POLLING-cleared state must be visible before we test - * NEED_RESCHED: - */ - smp_mb(); + if (cx->entry_method != ACPI_CSTATE_FFH) { + current_thread_info()->status &= ~TS_POLLING; + /* + * TS_POLLING-cleared state must be visible before we test + * NEED_RESCHED: + */ + smp_mb(); + } if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING; -- 1.6.0.6 -- 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/