From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932149AbVHMLie (ORCPT ); Sat, 13 Aug 2005 07:38:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932152AbVHMLie (ORCPT ); Sat, 13 Aug 2005 07:38:34 -0400 Received: from e32.co.us.ibm.com ([32.97.110.130]:31893 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S932149AbVHMLid (ORCPT ); Sat, 13 Aug 2005 07:38:33 -0400 Date: Sat, 13 Aug 2005 17:07:17 +0530 From: Srivatsa Vaddagiri To: Con Kolivas Cc: ck@vds.kolivas.org, tony@atomide.com, tuukka.tikkanen@elektrobit.com, akpm@osdl.org, johnstul@us.ibm.com, linux-kernel@vger.kernel.org, ak@muc.de, schwidefsky@de.ibm.com, george@mvista.com Subject: Re: [ck] [PATCH] dynamic-tick patch modified for SMP Message-ID: <20050813113717.GB4550@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <20050812201946.GA5327@in.ibm.com> <200508131135.46558.kernel@kolivas.org> <200508131651.08809.kernel@kolivas.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200508131651.08809.kernel@kolivas.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 13, 2005 at 04:51:07PM +1000, Con Kolivas wrote: > I'm sorry to say this doesn't appear to skip any ticks on my single P4 with > SMP/SMT enabled. Con, I had enabled skipping ticks only in default_idle routine. So if you have a different idle route (which I suspect is the case), it will not skip ticks (since dyn_tick_reprogram_timer will not be called). Can you try this patch? --- linux-2.6.13-rc6-root/arch/i386/kernel/process.c | 7 ++++--- linux-2.6.13-rc6-root/kernel/dyn-tick.c | 8 ++++++-- 2 files changed, 10 insertions(+), 5 deletions(-) diff -puN kernel/dyn-tick.c~dynamic-tick-smp-fix kernel/dyn-tick.c --- linux-2.6.13-rc6/kernel/dyn-tick.c~dynamic-tick-smp-fix 2005-08-13 15:53:56.000000000 +0530 +++ linux-2.6.13-rc6-root/kernel/dyn-tick.c 2005-08-13 15:56:12.000000000 +0530 @@ -37,16 +37,18 @@ spinlock_t dyn_tick_lock; /* * Arch independent code needed to reprogram next timer interrupt. - * Gets called with IRQs disabled from cpu_idle() before entering idle loop. + * Gets called from cpu_idle() before entering idle loop. */ unsigned long dyn_tick_reprogram_timer(void) { int cpu = smp_processor_id(); - unsigned long delta; + unsigned long delta, flags; if (!DYN_TICK_IS_SET(DYN_TICK_ENABLED)) return 0; + local_irq_save(flags); + if (rcu_pending(cpu) || local_softirq_pending()) return 0; @@ -76,6 +78,8 @@ unsigned long dyn_tick_reprogram_timer(v write_sequnlock(&xtime_lock); + local_irq_restore(flags); + return delta; } diff -puN arch/i386/kernel/process.c~dynamic-tick-smp-fix arch/i386/kernel/process.c --- linux-2.6.13-rc6/arch/i386/kernel/process.c~dynamic-tick-smp-fix 2005-08-13 15:53:56.000000000 +0530 +++ linux-2.6.13-rc6-root/arch/i386/kernel/process.c 2005-08-13 15:55:20.000000000 +0530 @@ -104,10 +104,9 @@ void default_idle(void) { if (!hlt_counter && boot_cpu_data.hlt_works_ok) { local_irq_disable(); - if (!need_resched()) { - dyn_tick_reprogram_timer(); + if (!need_resched()) safe_halt(); - } else + else local_irq_enable(); } else { cpu_relax(); @@ -202,6 +201,8 @@ void cpu_idle(void) if (cpu_is_offline(cpu)) play_dead(); + dyn_tick_reprogram_timer(); + __get_cpu_var(irq_stat).idle_timestamp = jiffies; idle(); } _ I have tested this patch on my Laptop (P4) that HZ goes down to ~25 with dyn-ticks enabled (but Power consumption goes _up_ as Ted had noted earlier - I need to try some of the ACPI patches that were pointed out in the thread). -- Thanks and Regards, Srivatsa Vaddagiri, Linux Technology Center, IBM Software Labs, Bangalore, INDIA - 560017