[ltt-dev] [UST PATCH] Add LTTng clock source support
Mathieu Desnoyers
mathieu.desnoyers at polymtl.ca
Tue Jan 11 11:51:19 EST 2011
* David Goulet (david.goulet at polymtl.ca) wrote:
> From: Julien Desfossez <julien.desfossez at polymtl.ca>
>
> At runtime, UST checks if the LTTng clock source is available
> If not, CLOCK_MONOTONIC is the default fallback.
>
> This makes UST use the LTTng kernel clock source. With this
> clock support, LTTng and UST traces are perfectly synchronize.
> Traces from these two tracer can be merged for analysis.
>
> LTTng 0.240 or higher is needed for this new clock source.
Looks good to me, but commit
commit 9dc7b7ff797a5cbb1e9ffd59e053a04562f306c4
Author: Nils Carlson <nils.carlson at ericsson.com>
Date: Wed Jan 5 13:53:43 2011 +0100
introduces hangs:
[pid 16533] writev(2, [{"ust-consumerd", 13}, {": ", 2},
{"error while loading shared libra"..., 36}, {": ", 2},
{"libustconsumer.so.0", 19}, {": ", 2}, {"cannot open shared
object file", 30}, {": ", 2}, {"No such file or directory",
25}, {"\n", 1}], 10) = 132
so I cannot test it here.
Mathieu
>
> Signed-off-by: David Goulet <david.goulet at polymtl.ca>
> ---
> include/ust/clock.h | 106 ++++++++++++++++++++++++++------------------------
> libust/tracectl.c | 10 +++++
> 2 files changed, 65 insertions(+), 51 deletions(-)
>
> diff --git a/include/ust/clock.h b/include/ust/clock.h
> index cb8a663..df56550 100644
> --- a/include/ust/clock.h
> +++ b/include/ust/clock.h
> @@ -15,8 +15,8 @@
> * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> */
>
> -#ifndef UST_CLOCK_H
> -#define UST_CLOCK_H
> +#ifndef _UST_CLOCK_H
> +#define _UST_CLOCK_H
>
> #include <time.h>
> #include <sys/time.h>
> @@ -29,56 +29,30 @@
> - gettimeofday() clock
>
> Microbenchmarks on Linux 2.6.30 on Core2 Duo 3GHz (functions are inlined):
> - Calls (100000000) to tsc(): 4004035641 cycles or 40 cycles/call
> - Calls (100000000) to gettimeofday(): 9723158352 cycles or 97 cycles/call
> + Calls (100000000) to tsc(): 4004035641 cycles or 40 cycles/call
> + Calls (100000000) to gettimeofday(): 9723158352 cycles or 97 cycles/call
>
> For merging traces with the kernel, a time source compatible with that of
> the kernel is necessary.
>
> Instead of gettimeofday(), we are now using clock_gettime for better
> precision and monotonicity.
> -
> */
>
> -#define TRACE_CLOCK_GENERIC
> -#ifdef TRACE_CLOCK_GENERIC
> -
> -static __inline__ u64 trace_clock_read64(void)
> -{
> +#if __i386__ || __x86_64__
> +/* Only available for x86 arch */
> +#define CLOCK_TRACE_FREQ 14
> +#define CLOCK_TRACE 15
> +union lttng_timespec {
> struct timespec ts;
> - u64 retval;
> -
> - clock_gettime(CLOCK_MONOTONIC, &ts);
> - retval = ts.tv_sec;
> - retval *= 1000000000;
> - retval += ts.tv_nsec;
> -
> - return retval;
> -}
> -
> -#else
> -
> -#if __i386 || __x86_64
> -
> -/* WARNING: Make sure to set frequency and scaling functions that will not
> - * result in lttv timestamps (sec.nsec) with seconds greater than 2**32-1.
> - */
> -static __inline__ u64 trace_clock_read64(void)
> -{
> - uint32_t low;
> - uint32_t high;
> - uint64_t retval;
> - __asm__ volatile ("rdtsc\n" : "=a" (low), "=d" (high));
> -
> - retval = high;
> - retval <<= 32;
> - return retval | low;
> -}
> -
> -#endif /* __i386 || __x86_64 */
> + u64 lttng_ts;
> +};
> +#endif /* __i386__ || __x86_64__ */
>
> -#ifdef __PPC__
> +static int ust_clock_source;
>
> +/* Choosing correct trace clock */
> +#if __PPC__
> static __inline__ u64 trace_clock_read64(void)
> {
> unsigned long tb_l;
> @@ -87,14 +61,14 @@ static __inline__ u64 trace_clock_read64(void)
> u64 tb;
>
> __asm__ (
> - "1:\n\t"
> - "mftbu %[rhigh]\n\t"
> - "mftb %[rlow]\n\t"
> - "mftbu %[rhigh2]\n\t"
> - "cmpw %[rhigh],%[rhigh2]\n\t"
> - "bne 1b\n\t"
> - : [rhigh] "=r" (tb_h), [rhigh2] "=r" (tb_h2), [rlow] "=r" (tb_l));
> -
> + "1:\n\t"
> + "mftbu %[rhigh]\n\t"
> + "mftb %[rlow]\n\t"
> + "mftbu %[rhigh2]\n\t"
> + "cmpw %[rhigh],%[rhigh2]\n\t"
> + "bne 1b\n\t"
> + : [rhigh] "=r" (tb_h), [rhigh2] "=r" (tb_h2), [rlow] "=r" (tb_l));
> +
> tb = tb_h;
> tb <<= 32;
> tb |= tb_l;
> @@ -102,12 +76,42 @@ static __inline__ u64 trace_clock_read64(void)
> return tb;
> }
>
> -#endif /* __PPC__ */
> +#else /* !__PPC__ */
>
> -#endif /* ! UST_TRACE_CLOCK_GENERIC */
> +static __inline__ u64 trace_clock_read64(void)
> +{
> + struct timespec ts;
> + u64 retval;
> + union lttng_timespec *lts = (union lttng_timespec *) &ts;
> +
> + clock_gettime(ust_clock_source, &ts);
> + /*
> + * Clock source can change when loading the binary (tracectl.c)
> + * so we must check if the clock source has changed before
> + * returning the correct value
> + */
> + if (likely(ust_clock_source == CLOCK_TRACE)) {
> + retval = lts->lttng_ts;
> + } else { /* CLOCK_MONOTONIC */
> + retval = ts.tv_sec;
> + retval *= 1000000000;
> + retval += ts.tv_nsec;
> + }
> +
> + return retval;
> +}
> +
> +#endif /* __PPC__ */
>
> static __inline__ u64 trace_clock_frequency(void)
> {
> + struct timespec ts;
> + union lttng_timespec *lts = (union lttng_timespec *) &ts;
> +
> + if (likely(ust_clock_source == CLOCK_TRACE)) {
> + clock_gettime(CLOCK_TRACE_FREQ, &ts);
> + return lts->lttng_ts;
> + }
> return 1000000000LL;
> }
>
> diff --git a/libust/tracectl.c b/libust/tracectl.c
> index b783c76..4f016bb 100644
> --- a/libust/tracectl.c
> +++ b/libust/tracectl.c
> @@ -39,6 +39,7 @@
> #include <ust/marker.h>
> #include <ust/tracepoint.h>
> #include <ust/tracectl.h>
> +#include <ust/clock.h>
> #include "tracer.h"
> #include "usterr.h"
> #include "ustcomm.h"
> @@ -1262,6 +1263,15 @@ static void __attribute__((constructor)) init()
>
> create_listener();
>
> + /* Get clock the clock source type */
> + struct timespec ts;
> + /* Default clock source */
> + ust_clock_source = CLOCK_TRACE;
> + if (clock_gettime(ust_clock_source, &ts) != 0) {
> + ust_clock_source = CLOCK_MONOTONIC;
> + DBG("UST traces will not be synchronized with LTTng traces");
> + }
> +
> autoprobe_val = getenv("UST_AUTOPROBE");
> if (autoprobe_val) {
> struct marker_iter iter;
> --
> 1.7.3.5
>
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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