From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965371AbXGSRJO (ORCPT ); Thu, 19 Jul 2007 13:09:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S940314AbXGSRHs (ORCPT ); Thu, 19 Jul 2007 13:07:48 -0400 Received: from mail.tmr.com ([64.65.253.246]:44216 "EHLO posidon.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S940294AbXGSRHr (ORCPT ); Thu, 19 Jul 2007 13:07:47 -0400 Message-ID: <469F9A2E.5020107@tmr.com> Date: Thu, 19 Jul 2007 13:06:54 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.4) Gecko/20070509 SeaMonkey/1.1.2 MIME-Version: 1.0 To: Ingo Molnar CC: davidsen@posidon.tmr.com, Linus Torvalds , Ian Kent , Chuck Ebbert , linux-kernel@vger.kernel.org Subject: Re: [patch] CFS scheduler, -v19 References: <1184054902.12336.19.camel@Homer.simpson.net> <469512C1.6090406@tmr.com> <20070711205556.GA27266@elte.hu> <4697EC49.4070303@tmr.com> <469BE462.9030004@redhat.com> <20070716215541.GA27171@elte.hu> <1184648474.3188.33.camel@raven.themaw.net> <20070717074537.GA13539@elte.hu> <469E8821.3070700@tmr.com> <20070719143214.GA6387@elte.hu> In-Reply-To: <20070719143214.GA6387@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > * Bill Davidsen wrote: > >>> Does the patch below help? Doesn't seem to apply against 2.6.22.1, I'm trying 2.6.22.6 as soon as I recreate it. >> Spectacularly no! With this patch the "glitch1" script with multiple >> scrolling windows has all xterms and glxgears stop totally dead for >> ~200ms once per second. I didn't properly test anything else after >> that. > > Bill, could you try the patch below - does it fix the automount problem, > without introducing new problems? > > Ingo > > ---------------> > Subject: time: introduce xtime_seconds > From: Ingo Molnar > > introduce the xtime_seconds optimization. This is a read-mostly > low-resolution time source available to sys_time() and kernel-internal > use. This variable is kept uptodate atomically, and it's monotically > increased, every time some time interface constructs an xtime-alike time > result that overflows the seconds value. (it's updated from the timer > interrupt as well) > > this way high-resolution time results update their seconds component at > the same time sys_time() does it: > > 1184858832999989000 > 1184858832000000000 > 1184858832999992000 > 1184858832000000000 > 1184858832999996000 > 1184858832000000000 > 1184858832999999000 > 1184858832000000000 > 1184858833000003000 > 1184858833000000000 > 1184858833000006000 > 1184858833000000000 > 1184858833000009000 > 1184858833000000000 > > [ these are nsec time results from alternating calls to sys_time() and > sys_gettimeofday(), recorded at the seconds boundary. ] > > instead of the previous (non-coherent) behavior: > > 1184848950999987000 > 1184848950000000000 > 1184848950999990000 > 1184848950000000000 > 1184848950999994000 > 1184848950000000000 > 1184848950999997000 > 1184848950000000000 > 1184848951000001000 > 1184848950000000000 > 1184848951000005000 > 1184848950000000000 > 1184848951000008000 > 1184848950000000000 > 1184848951000011000 > 1184848950000000000 > 1184848951000015000 > > Signed-off-by: Ingo Molnar > --- > include/linux/time.h | 13 +++++++++++-- > kernel/time.c | 25 ++++++------------------- > kernel/time/timekeeping.c | 28 ++++++++++++++++++++++++---- > 3 files changed, 41 insertions(+), 25 deletions(-) > > Index: linux/include/linux/time.h > =================================================================== > --- linux.orig/include/linux/time.h > +++ linux/include/linux/time.h > @@ -91,19 +91,28 @@ static inline struct timespec timespec_s > extern struct timespec xtime; > extern struct timespec wall_to_monotonic; > extern seqlock_t xtime_lock __attribute__((weak)); > +extern unsigned long xtime_seconds; > > extern unsigned long read_persistent_clock(void); > void timekeeping_init(void); > > +extern void __update_xtime_seconds(unsigned long new_xtime_seconds); > + > +static inline void update_xtime_seconds(unsigned long new_xtime_seconds) > +{ > + if (unlikely((long)(new_xtime_seconds - xtime_seconds) > 0)) > + __update_xtime_seconds(new_xtime_seconds); > +} > + > static inline unsigned long get_seconds(void) > { > - return xtime.tv_sec; > + return xtime_seconds; > } > > struct timespec current_kernel_time(void); > > #define CURRENT_TIME (current_kernel_time()) > -#define CURRENT_TIME_SEC ((struct timespec) { xtime.tv_sec, 0 }) > +#define CURRENT_TIME_SEC ((struct timespec) { xtime_seconds, 0 }) > > extern void do_gettimeofday(struct timeval *tv); > extern int do_settimeofday(struct timespec *tv); > Index: linux/kernel/time.c > =================================================================== > --- linux.orig/kernel/time.c > +++ linux/kernel/time.c > @@ -58,11 +58,10 @@ EXPORT_SYMBOL(sys_tz); > asmlinkage long sys_time(time_t __user * tloc) > { > /* > - * We read xtime.tv_sec atomically - it's updated > - * atomically by update_wall_time(), so no need to > - * even read-lock the xtime seqlock: > + * We read xtime_seconds atomically - it's updated > + * atomically by update_xtime_seconds(): > */ > - time_t i = xtime.tv_sec; > + time_t i = xtime_seconds; > > smp_rmb(); /* sys_time() results are coherent */ > > @@ -226,11 +225,11 @@ inline struct timespec current_kernel_ti > > do { > seq = read_seqbegin(&xtime_lock); > - > + > now = xtime; > } while (read_seqretry(&xtime_lock, seq)); > > - return now; > + return now; > } > > EXPORT_SYMBOL(current_kernel_time); > @@ -377,19 +376,7 @@ void do_gettimeofday (struct timeval *tv > tv->tv_sec = sec; > tv->tv_usec = usec; > > - /* > - * Make sure xtime.tv_sec [returned by sys_time()] always > - * follows the gettimeofday() result precisely. This > - * condition is extremely unlikely, it can hit at most > - * once per second: > - */ > - if (unlikely(xtime.tv_sec != tv->tv_sec)) { > - unsigned long flags; > - > - write_seqlock_irqsave(&xtime_lock, flags); > - update_wall_time(); > - write_sequnlock_irqrestore(&xtime_lock, flags); > - } > + update_xtime_seconds(sec); > } > EXPORT_SYMBOL(do_gettimeofday); > > Index: linux/kernel/time/timekeeping.c > =================================================================== > --- linux.orig/kernel/time/timekeeping.c > +++ linux/kernel/time/timekeeping.c > @@ -45,14 +45,27 @@ EXPORT_SYMBOL(xtime_lock); > * used instead. > */ > struct timespec xtime __attribute__ ((aligned (16))); > -struct timespec wall_to_monotonic __attribute__ ((aligned (16))); > -static unsigned long total_sleep_time; /* seconds */ > - > EXPORT_SYMBOL(xtime); > > +struct timespec wall_to_monotonic __attribute__ ((aligned (16))) __read_mostly; > +static unsigned long total_sleep_time __read_mostly; /* seconds */ > + > +unsigned long xtime_seconds __read_mostly; > + > +/* pointer to current clocksource: */ > +static struct clocksource *clock __read_mostly; > > -static struct clocksource *clock; /* pointer to current clocksource */ > +/* > + * Called when either xtime or any xtime-alike result back to > + * user-space overflows the xtime_seconds field: > + */ > +void __update_xtime_seconds(unsigned long new_xtime_seconds) > +{ > + unsigned long old_xtime_seconds = xtime_seconds; > > + if ((long)(new_xtime_seconds - old_xtime_seconds) > 0) > + cmpxchg(&xtime_seconds, old_xtime_seconds, new_xtime_seconds); > +} > > #ifdef CONFIG_GENERIC_TIME > /** > @@ -100,6 +113,8 @@ static inline void __get_realtime_clock_ > } while (read_seqretry(&xtime_lock, seq)); > > timespec_add_ns(ts, nsecs); > + > + update_xtime_seconds(ts->tv_sec); > } > > /** > @@ -256,6 +271,8 @@ void __init timekeeping_init(void) > clock->cycle_last = clocksource_read(clock); > > xtime.tv_sec = sec; > + update_xtime_seconds(sec); > + > xtime.tv_nsec = 0; > set_normalized_timespec(&wall_to_monotonic, > -xtime.tv_sec, -xtime.tv_nsec); > @@ -290,6 +307,8 @@ static int timekeeping_resume(struct sys > unsigned long sleep_length = now - timekeeping_suspend_time; > > xtime.tv_sec += sleep_length; > + update_xtime_seconds(xtime.tv_sec); > + > wall_to_monotonic.tv_sec -= sleep_length; > total_sleep_time += sleep_length; > } > @@ -464,6 +483,7 @@ void update_wall_time(void) > clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift; > xtime.tv_sec++; > second_overflow(); > + update_xtime_seconds(xtime.tv_sec); > } > > /* interpolator bits */ >