Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756592AbZGGMHc (ORCPT ); Tue, 7 Jul 2009 08:07:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754708AbZGGMHV (ORCPT ); Tue, 7 Jul 2009 08:07:21 -0400 Received: from hera.kernel.org ([140.211.167.34]:56248 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754694AbZGGMHV (ORCPT ); Tue, 7 Jul 2009 08:07:21 -0400 Date: Tue, 7 Jul 2009 12:06:51 GMT From: tip-bot for Martin Schwidefsky To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, johnstul@us.ibm.com, schwidefsky@de.ibm.com, tglx@linutronix.de Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, johnstul@us.ibm.com, schwidefsky@de.ibm.com, tglx@linutronix.de In-Reply-To: <20090707112728.3005244d@skybase> References: <20090707112728.3005244d@skybase> Subject: [tip:timers/core] timekeeping: optimized ktime_get[_ts] for GENERIC_TIME=y Message-ID: Git-Commit-ID: 951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32 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]); Tue, 07 Jul 2009 12:06:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5250 Lines: 175 Commit-ID: 951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32 Gitweb: http://git.kernel.org/tip/951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32 Author: Martin Schwidefsky AuthorDate: Tue, 7 Jul 2009 11:27:28 +0200 Committer: Thomas Gleixner CommitDate: Tue, 7 Jul 2009 12:47:33 +0200 timekeeping: optimized ktime_get[_ts] for GENERIC_TIME=y The generic ktime_get function defined in kernel/hrtimer.c is suboptimial for GENERIC_TIME=y: 0) | ktime_get() { 0) | ktime_get_ts() { 0) | getnstimeofday() { 0) | read_tod_clock() { 0) 0.601 us | } 0) 1.938 us | } 0) | set_normalized_timespec() { 0) 0.602 us | } 0) 4.375 us | } 0) 5.523 us | } Overall there are two read_seqbegin/read_seqretry loops and a lot of unnecessary struct timespec calculations. ktime_get returns a nano second value which is the sum of xtime, wall_to_monotonic and the nano second delta from the clock source. ktime_get can be optimized for GENERIC_TIME=y. The new version only calls clocksource_read: 0) | ktime_get() { 0) | read_tod_clock() { 0) 0.610 us | } 0) 1.977 us | } It uses a single read_seqbegin/readseqretry loop and just adds everthing to a nano second value. ktime_get_ts is optimized in a similar fashion. [ tglx: added WARN_ON(timekeeping_suspended) as in getnstimeofday() ] Signed-off-by: Martin Schwidefsky Acked-by: john stultz LKML-Reference: <20090707112728.3005244d@skybase> Signed-off-by: Thomas Gleixner --- kernel/hrtimer.c | 4 ++ kernel/time/timekeeping.c | 69 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 73 insertions(+), 0 deletions(-) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 9002958..829e066 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -48,6 +48,7 @@ #include +#ifndef CONFIG_GENERIC_TIME /** * ktime_get - get the monotonic time in ktime_t format * @@ -62,6 +63,7 @@ ktime_t ktime_get(void) return timespec_to_ktime(now); } EXPORT_SYMBOL_GPL(ktime_get); +#endif /** * ktime_get_real - get the real (wall-) time in ktime_t format @@ -106,6 +108,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) = } }; +#ifndef CONFIG_GENERIC_TIME /** * ktime_get_ts - get the monotonic clock in timespec format * @ts: pointer to timespec variable @@ -130,6 +133,7 @@ void ktime_get_ts(struct timespec *ts) ts->tv_nsec + tomono.tv_nsec); } EXPORT_SYMBOL_GPL(ktime_get_ts); +#endif /* * Get the coarse grained time at the softirq based on xtime and diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index e8c77d9..7a24813 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -125,6 +125,75 @@ void getnstimeofday(struct timespec *ts) EXPORT_SYMBOL(getnstimeofday); +ktime_t ktime_get(void) +{ + cycle_t cycle_now, cycle_delta; + unsigned int seq; + s64 secs, nsecs; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqbegin(&xtime_lock); + secs = xtime.tv_sec + wall_to_monotonic.tv_sec; + nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec; + + /* read clocksource: */ + cycle_now = clocksource_read(clock); + + /* calculate the delta since the last update_wall_time: */ + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; + + /* convert to nanoseconds: */ + nsecs += cyc2ns(clock, cycle_delta); + + } while (read_seqretry(&xtime_lock, seq)); + /* + * Use ktime_set/ktime_add_ns to create a proper ktime on + * 32-bit architectures without CONFIG_KTIME_SCALAR. + */ + return ktime_add_ns(ktime_set(secs, 0), nsecs); +} +EXPORT_SYMBOL_GPL(ktime_get); + +/** + * ktime_get_ts - get the monotonic clock in timespec format + * @ts: pointer to timespec variable + * + * The function calculates the monotonic clock from the realtime + * clock and the wall_to_monotonic offset and stores the result + * in normalized timespec format in the variable pointed to by @ts. + */ +void ktime_get_ts(struct timespec *ts) +{ + cycle_t cycle_now, cycle_delta; + struct timespec tomono; + unsigned int seq; + s64 nsecs; + + WARN_ON(timekeeping_suspended); + + do { + seq = read_seqbegin(&xtime_lock); + *ts = xtime; + tomono = wall_to_monotonic; + + /* read clocksource: */ + cycle_now = clocksource_read(clock); + + /* calculate the delta since the last update_wall_time: */ + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; + + /* convert to nanoseconds: */ + nsecs = cyc2ns(clock, cycle_delta); + + } while (read_seqretry(&xtime_lock, seq)); + + set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec, + ts->tv_nsec + tomono.tv_nsec + nsecs); +} +EXPORT_SYMBOL_GPL(ktime_get_ts); + /** * do_gettimeofday - Returns the time of day in a timeval * @tv: pointer to the timeval to be set -- 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/