From: Zachary Amsden <zamsden@redhat.com>
To: Glauber Costa <glommer@redhat.com>
Cc: kvm@vger.kernel.org, avi@redhat.com, mtosatti@redhat.com,
riel@redhat.com, peterz@infradead.org, mingo@elte.hu,
jeremy@goop.org
Subject: Re: [RFC 1/8] Implement getnsboottime kernel API
Date: Wed, 01 Sep 2010 13:56:17 -1000 [thread overview]
Message-ID: <4C7EE821.8030804@redhat.com> (raw)
In-Reply-To: <1283184391-7785-3-git-send-email-glommer@redhat.com>
On 08/30/2010 06:06 AM, Glauber Costa wrote:
> From: Zachary Amsden<zamsden@redhat.com>
>
> Add a kernel call to get the number of nanoseconds since boot. This
> is generally useful enough to make it a generic call.
>
> Signed-off-by: Zachary Amsden<zamsden@redhat.com>
> ---
> include/linux/time.h | 1 +
> kernel/time/timekeeping.c | 27 +++++++++++++++++++++++++++
> 2 files changed, 28 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/time.h b/include/linux/time.h
> index ea3559f..5d04108 100644
> --- a/include/linux/time.h
> +++ b/include/linux/time.h
> @@ -145,6 +145,7 @@ extern void getnstimeofday(struct timespec *tv);
> extern void getrawmonotonic(struct timespec *ts);
> extern void getboottime(struct timespec *ts);
> extern void monotonic_to_bootbased(struct timespec *ts);
> +extern s64 getnsboottime(void);
>
> extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
> extern int timekeeping_valid_for_hres(void);
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index caf8d4d..d250f0a 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -285,6 +285,33 @@ void ktime_get_ts(struct timespec *ts)
> }
> EXPORT_SYMBOL_GPL(ktime_get_ts);
>
> +
> +/**
> + * getnsboottime - get the bootbased clock in nsec format
> + *
> + * The function calculates the bootbased 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.
> + */
> +s64 getnsboottime(void)
> +{
> + 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;
> + secs += total_sleep_time.tv_sec;
> + nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
> + nsecs += total_sleep_time.tv_nsec + timekeeping_get_ns();
> +
> + } while (read_seqretry(&xtime_lock, seq));
> + return nsecs + (secs * NSEC_PER_SEC);
> +}
> +EXPORT_SYMBOL_GPL(getnsboottime);
> +
> /**
> * do_gettimeofday - Returns the time of day in a timeval
> * @tv: pointer to the timeval to be set
>
FWIW, I sent a patch to drop this yesterday, in favor of this approach:
+static inline u64 get_kernel_ns(void)
+{
+ struct timespec ts;
+
+ WARN_ON(preemptible());
+ ktime_get_ts(&ts);
+ monotonic_to_bootbased(&ts);
+ return timespec_to_ns(&ts);
+}
+
next prev parent reply other threads:[~2010-09-01 23:56 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-30 16:06 [RFC v2 0/7] kvm stael time implementation Glauber Costa
2010-08-30 16:06 ` [RFC v2 1/7] change headers preparing for steal time Glauber Costa
2010-08-30 16:06 ` [RFC 1/8] Implement getnsboottime kernel API Glauber Costa
2010-08-30 16:06 ` [RFC v2 2/7] always call kvm_write_guest Glauber Costa
2010-08-30 16:06 ` [RFC 2/8] change headers preparing for steal time Glauber Costa
2010-08-30 16:06 ` [RFC 3/8] always call kvm_write_guest Glauber Costa
2010-08-30 16:06 ` [RFC v2 3/7] measure time out of guest Glauber Costa
2010-08-30 16:06 ` [RFC v2 4/7] change kernel accounting to include steal time Glauber Costa
2010-08-30 16:06 ` [RFC 4/8] measure time out of guest Glauber Costa
2010-08-30 16:06 ` [RFC 5/8] change kernel accounting to include steal time Glauber Costa
2010-08-30 16:06 ` [RFC v2 5/7] kvm steal time implementation Glauber Costa
2010-08-30 16:06 ` [RFC 6/8] " Glauber Costa
2010-08-30 16:06 ` [RFC v2 6/7] touch softlockup watchdog Glauber Costa
2010-08-30 16:06 ` [RFC v2 7/7] tell guest about steal time feature Glauber Costa
2010-08-30 16:06 ` [RFC 7/8] touch softlockup watchdog Glauber Costa
2010-08-30 16:06 ` [RFC 8/8] tell guest about steal time feature Glauber Costa
2010-08-30 17:33 ` [RFC v2 6/7] touch softlockup watchdog Jeremy Fitzhardinge
2010-08-30 18:07 ` Glauber Costa
2010-08-30 16:46 ` [RFC 5/8] change kernel accounting to include steal time Peter Zijlstra
2010-08-30 17:26 ` Glauber Costa
2010-08-30 17:30 ` [RFC v2 4/7] " Jeremy Fitzhardinge
2010-08-30 18:39 ` Rik van Riel
2010-08-30 19:07 ` Jeremy Fitzhardinge
2010-08-30 19:14 ` Peter Zijlstra
2010-08-30 19:17 ` Rik van Riel
2010-08-30 19:20 ` Peter Zijlstra
2010-08-30 19:45 ` Rik van Riel
2010-08-30 22:56 ` Jeremy Fitzhardinge
2010-08-30 23:03 ` Rik van Riel
2010-08-31 8:11 ` Peter Zijlstra
2010-09-02 18:19 ` Glauber Costa
2010-09-03 3:24 ` Jeremy Fitzhardinge
2010-09-03 7:18 ` Peter Zijlstra
2010-09-01 23:56 ` Zachary Amsden [this message]
2010-08-30 16:37 ` [RFC v2 0/7] kvm stael time implementation Peter Zijlstra
2010-08-30 16:45 ` Jeremy Fitzhardinge
2010-08-30 17:21 ` Glauber Costa
2010-08-30 17:20 ` Jeremy Fitzhardinge
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