Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757161AbYGNJ64 (ORCPT ); Mon, 14 Jul 2008 05:58:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756330AbYGNJ6s (ORCPT ); Mon, 14 Jul 2008 05:58:48 -0400 Received: from web32608.mail.mud.yahoo.com ([68.142.207.235]:46730 "HELO web32608.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755887AbYGNJ6r (ORCPT ); Mon, 14 Jul 2008 05:58:47 -0400 X-Greylist: delayed 399 seconds by postgrey-1.27 at vger.kernel.org; Mon, 14 Jul 2008 05:58:47 EDT X-Mailer: YahooMailRC/1042.40 YahooMailWebService/0.7.199 Date: Mon, 14 Jul 2008 02:52:07 -0700 (PDT) From: Martin Knoblauch Reply-To: Martin Knoblauch Subject: [Patch 2.6.26] Fix prinkt timesamps for good [was: [Bug 10648] CONFIG_PRINTK_TIME broken on git HEAD ?] To: Peter Zijlstra , linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="0-1812908930-1216029127=:97482" Message-ID: <717386.97482.qm@web32608.mail.mud.yahoo.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11088 Lines: 263 --0-1812908930-1216029127=:97482 Content-Type: text/plain; charset=us-ascii ----- Original Message ---- > From: Peter Zijlstra > To: Martin Knoblauch > Sent: Tuesday, June 10, 2008 10:08:39 AM > Subject: Re: [Bug 10648] CONFIG_PRINTK_TIME broken on git HEAD ? > > On Tue, 2008-06-10 at 01:03 -0700, Martin Knoblauch wrote: > > ----- Original Message ---- > > > > > From: Peter Zijlstra > > > To: Martin Knoblauch > > > Sent: Monday, June 9, 2008 5:18:05 PM > > > Subject: Re: [Bug 10648] CONFIG_PRINTK_TIME broken on git HEAD ? > > > > > > On Mon, 2008-06-09 at 08:13 -0700, Martin Knoblauch wrote: > > > > Hi Peter, > > > > > > > > could you please send me that patch as an attachment. My mail agent > mangles > > > the bloody thing beyond recognition .... > > > > > > here goes > > Hi Peter, > > > > the patch is for 2.6.26 correct? First I assumed it is the backport > > to 2.6.25, but apparently that does not have kernel/sched_clock.c. In > > any case, applying to 2.6.26-rc5 works fine and the result is great. > > Timestamps are monotonic and correspond to the first number in > > "/proc/uptime" much better than ever before. Great work. If this goes > > into 2.6.26, I will [try to] prepare a patch against 2.6.25. > > Hmm, the patch might be a tad to big for .26 at this point, but I'll see > what I can do to make .26 a better kernel ;-) > > Thanks for testing! Hi Peter, now that 2.6.26 is released you may want to push the patch to fix the print-timestamps for good. I have rebased your patch to 2.6.26 and it works as expected. printk-timestamps are now monotonic and show "uptime" within millisecond accuracy. This is IMO also material for 2.6.26-stable. To fix it for 2.6.25 seems more involved and I do not personally see the urgency Cheers Martin Tested-by: Martin Knoblauch diff -urp linux-2.6.26-orig/kernel/sched.c linux-2.6.26-sched-clock/kernel/sched.c --- linux-2.6.26-orig/kernel/sched.c 2008-07-13 23:51:29.000000000 +0200 +++ linux-2.6.26-sched-clock/kernel/sched.c 2008-07-14 10:25:15.000000000 +0200 @@ -754,8 +754,6 @@ const_debug unsigned int sysctl_sched_nr */ unsigned int sysctl_sched_rt_period = 1000000; -static __read_mostly int scheduler_running; - /* * part of the period that we allow rt tasks to run in us. * default: 0.95s @@ -775,82 +773,6 @@ static inline u64 global_rt_runtime(void return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC; } -unsigned long long time_sync_thresh = 100000; - -static DEFINE_PER_CPU(unsigned long long, time_offset); -static DEFINE_PER_CPU(unsigned long long, prev_cpu_time); - -/* - * Global lock which we take every now and then to synchronize - * the CPUs time. This method is not warp-safe, but it's good - * enough to synchronize slowly diverging time sources and thus - * it's good enough for tracing: - */ -static DEFINE_SPINLOCK(time_sync_lock); -static unsigned long long prev_global_time; - -static unsigned long long __sync_cpu_clock(unsigned long long time, int cpu) -{ - /* - * We want this inlined, to not get tracer function calls - * in this critical section: - */ - spin_acquire(&time_sync_lock.dep_map, 0, 0, _THIS_IP_); - __raw_spin_lock(&time_sync_lock.raw_lock); - - if (time < prev_global_time) { - per_cpu(time_offset, cpu) += prev_global_time - time; - time = prev_global_time; - } else { - prev_global_time = time; - } - - __raw_spin_unlock(&time_sync_lock.raw_lock); - spin_release(&time_sync_lock.dep_map, 1, _THIS_IP_); - - return time; -} - -static unsigned long long __cpu_clock(int cpu) -{ - unsigned long long now; - - /* - * Only call sched_clock() if the scheduler has already been - * initialized (some code might call cpu_clock() very early): - */ - if (unlikely(!scheduler_running)) - return 0; - - now = sched_clock_cpu(cpu); - - return now; -} - -/* - * For kernel-internal use: high-speed (but slightly incorrect) per-cpu - * clock constructed from sched_clock(): - */ -unsigned long long cpu_clock(int cpu) -{ - unsigned long long prev_cpu_time, time, delta_time; - unsigned long flags; - - local_irq_save(flags); - prev_cpu_time = per_cpu(prev_cpu_time, cpu); - time = __cpu_clock(cpu) + per_cpu(time_offset, cpu); - delta_time = time-prev_cpu_time; - - if (unlikely(delta_time > time_sync_thresh)) { - time = __sync_cpu_clock(time, cpu); - per_cpu(prev_cpu_time, cpu) = time; - } - local_irq_restore(flags); - - return time; -} -EXPORT_SYMBOL_GPL(cpu_clock); - #ifndef prepare_arch_switch # define prepare_arch_switch(next) do { } while (0) #endif @@ -7858,8 +7780,6 @@ void __init sched_init(void) * During early bootup we pretend to be a normal task: */ current->sched_class = &fair_sched_class; - - scheduler_running = 1; } #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP diff -urp linux-2.6.26-orig/kernel/sched_clock.c linux-2.6.26-sched-clock/kernel/sched_clock.c --- linux-2.6.26-orig/kernel/sched_clock.c 2008-07-13 23:51:29.000000000 +0200 +++ linux-2.6.26-sched-clock/kernel/sched_clock.c 2008-07-14 10:25:15.000000000 +0200 @@ -244,3 +244,15 @@ unsigned long long __attribute__((weak)) { return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); } + +unsigned long long cpu_clock(int cpu) +{ + unsigned long long clock; + unsigned long flags; + + raw_local_irq_save(flags); + clock = sched_clock_cpu(cpu); + raw_local_irq_restore(flags); + + return clock; +} --0-1812908930-1216029127=:97482 Content-Type: text/x-patch; name="printk-timestamp-2.6.26.patch" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="printk-timestamp-2.6.26.patch" ZGlmZiAtdXJwIGxpbnV4LTIuNi4yNi1vcmlnL2tlcm5lbC9zY2hlZC5jIGxp bnV4LTIuNi4yNi1zY2hlZC1jbG9jay9rZXJuZWwvc2NoZWQuYwotLS0gbGlu 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