[ltt-dev] (forw) [RFC patch 08/15] LTTng - Timestamping
Mathieu Desnoyers
compudj at krystal.dyndns.org
Mon Oct 20 11:49:11 EDT 2008
Yeah, well I had this stuff in the LTTng tree for about 3 years, so I
kept everything under my own namespace. I like Ingo's idea of
"trace_clock()". I'll probably change the namespace to this, and move
the files from /ltt/* to /kernel/trace/*.
Mathieu
* Masami Hiramatsu (mhiramat at redhat.com) wrote:
> Hi Mathieu,
>
> These patches seems generally good. However, I wonder why you added
> "ltt_" prefix. if it was useful for other parts of the kernel
> (I think so), more general name(generic_timestamp?) would be preferable :)
>
> Thank you,
>
> Mathieu Desnoyers wrote:
>> Hello,
>> Too many CCs on this last post. I should probably have added some, but
>> here is a link to the thread :
>> http://lkml.org/lkml/2008/10/16/511
>> Comments are welcome.
>> Mathieu
>> ----- Forwarded message from Mathieu Desnoyers
>> <mathieu.desnoyers at polymtl.ca> -----
>> Date: Thu, 16 Oct 2008 19:27:37 -0400
>> To: Linus Torvalds <torvalds at linux-foundation.org>,
>> Andrew Morton <akpm at linux-foundation.org>,
>> Ingo Molnar <mingo at elte.hu>, linux-kernel at vger.kernel.org,
>> linux-arch at vger.kernel.org, Steven Rostedt <rostedt at goodmis.org>,
>> Peter Zijlstra <a.p.zijlstra at chello.nl>,
>> Thomas Gleixner <tglx at linutronix.de>
>> Cc: David Miller <davem at davemloft.net>,
>> Mathieu Desnoyers <mathieu.desnoyers at polymtl.ca>,
>> Ralf Baechle <ralf at linux-mips.org>, benh at kernel.crashing.org,
>> paulus at samba.org, Ingo Molnar <mingo at redhat.com>
>> User-Agent: quilt/0.46-1
>> From: Mathieu Desnoyers <mathieu.desnoyers at polymtl.ca>
>> Subject: [RFC patch 08/15] LTTng - Timestamping
>> Wrapper to use the lower level clock sources available on the systems.
>> Fall-back
>> on jiffies or'd with a logical clock for architectures lacking CPU
>> timestamp
>> counters. Fall-back on a mixed TSC-logical clock on architectures lacking
>> synchronized TSC on SMP.
>> A generic fallback based on a logical clock and the timer interrupt is
>> available.
>> generic - Uses jiffies or'd with a logical clock extended to 64 bits by
>> ltt-timestamp.c.
>> i386 - Uses TSC. If detects non synchronized TSC, uses mixed TSC-logical
>> clock.
>> mips - Uses TSC extended atomically from 32 to 64 bits by ltt-heartbeat.c.
>> powerpc - Uses TSC or generic ltt clock.
>> x86_64 - Uses TSC. If detects non synchronized TSC, uses mixed TSC-logical
>> clock
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at polymtl.ca>
>> CC: Ralf Baechle <ralf at linux-mips.org>
>> CC: benh at kernel.crashing.org
>> CC: paulus at samba.org
>> CC: David Miller <davem at davemloft.net>
>> CC: Linus Torvalds <torvalds at linux-foundation.org>
>> CC: Andrew Morton <akpm at linux-foundation.org>
>> CC: Ingo Molnar <mingo at redhat.com>
>> CC: Peter Zijlstra <a.p.zijlstra at chello.nl>
>> CC: Thomas Gleixner <tglx at linutronix.de>
>> CC: Steven Rostedt <rostedt at goodmis.org>
>> CC: linux-arch at vger.kernel.org
>> ---
>> include/asm-generic/ltt.h | 53
>> ++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/ltt.h | 27 +++++++++++++++++++++++
>> kernel/timer.c | 2 +
>> 3 files changed, 82 insertions(+)
>> Index: linux-2.6-lttng/kernel/timer.c
>> ===================================================================
>> --- linux-2.6-lttng.orig/kernel/timer.c 2008-09-16 14:50:15.000000000
>> -0400
>> +++ linux-2.6-lttng/kernel/timer.c 2008-09-16 14:59:17.000000000 -0400
>> @@ -37,6 +37,7 @@
>> #include <linux/delay.h>
>> #include <linux/tick.h>
>> #include <linux/kallsyms.h>
>> +#include <linux/ltt.h>
>> #include <asm/uaccess.h>
>> #include <asm/unistd.h>
>> @@ -1066,6 +1067,7 @@ void do_timer(unsigned long ticks)
>> {
>> jiffies_64 += ticks;
>> update_times(ticks);
>> + ltt_add_timestamp(ticks);
>> }
>> #ifdef __ARCH_WANT_SYS_ALARM
>> Index: linux-2.6-lttng/include/linux/ltt.h
>> ===================================================================
>> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
>> +++ linux-2.6-lttng/include/linux/ltt.h 2008-09-16 14:58:47.000000000
>> -0400
>> @@ -0,0 +1,27 @@
>> +#ifndef _LINUX_LTT_H
>> +#define _LINUX_LTT_H
>> +
>> +/*
>> + * Generic LTT clock.
>> + *
>> + * Chooses between an architecture specific clock or an atomic logical
>> clock.
>> + *
>> + * Copyright (C) 2007 Mathieu Desnoyers (mathieu.desnoyers at polymtl.ca)
>> + */
>> +
>> +#ifdef CONFIG_LTT_TIMESTAMP
>> +#ifdef CONFIG_HAVE_LTT_CLOCK
>> +#include <asm/ltt.h>
>> +#else
>> +#include <asm-generic/ltt.h>
>> +
>> +#define ltt_get_timestamp32 ltt_get_timestamp32_generic
>> +#define ltt_get_timestamp64 ltt_get_timestamp64_generic
>> +#define ltt_add_timestamp ltt_add_timestamp_generic
>> +#define ltt_frequency ltt_frequency_generic
>> +#define ltt_freq_scale ltt_freq_scale_generic
>> +#endif /* CONFIG_HAVE_LTT_CLOCK */
>> +#else
>> +#define ltt_add_timestamp(ticks)
>> +#endif /* CONFIG_LTT_TIMESTAMP */
>> +#endif /* _LINUX_LTT_H */
>> Index: linux-2.6-lttng/include/asm-generic/ltt.h
>> ===================================================================
>> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
>> +++ linux-2.6-lttng/include/asm-generic/ltt.h 2008-09-16
>> 14:58:47.000000000 -0400
>> @@ -0,0 +1,53 @@
>> +#ifndef _ASM_GENERIC_LTT_H
>> +#define _ASM_GENERIC_LTT_H
>> +
>> +/*
>> + * linux/include/asm-generic/ltt.h
>> + *
>> + * Copyright (C) 2007 - Mathieu Desnoyers (mathieu.desnoyers at polymtl.ca)
>> + *
>> + * Generic definitions for LTT
>> + * Architectures without TSC
>> + */
>> +
>> +#include <linux/param.h> /* For HZ */
>> +#include <asm/atomic.h>
>> +
>> +#define LTT_GENERIC_CLOCK_SHIFT 13
>> +
>> +u64 ltt_read_synthetic_tsc(void);
>> +
>> +extern atomic_t lttng_generic_clock;
>> +
>> +static inline u32 ltt_get_timestamp32_generic(void)
>> +{
>> + return atomic_add_return(1, <tng_generic_clock);
>> +}
>> +
>> +static inline u64 ltt_get_timestamp64_generic(void)
>> +{
>> + return ltt_read_synthetic_tsc();
>> +}
>> +
>> +static inline void ltt_add_timestamp_generic(unsigned long ticks)
>> +{
>> + int old_clock, new_clock;
>> +
>> + do {
>> + old_clock = atomic_read(<tng_generic_clock);
>> + new_clock = (old_clock + (ticks << LTT_GENERIC_CLOCK_SHIFT))
>> + & (~((1 << LTT_GENERIC_CLOCK_SHIFT) - 1));
>> + } while (atomic_cmpxchg(<tng_generic_clock, old_clock, new_clock)
>> + != old_clock);
>> +}
>> +
>> +static inline unsigned int ltt_frequency_generic(void)
>> +{
>> + return HZ << LTT_GENERIC_CLOCK_SHIFT;
>> +}
>> +
>> +static inline u32 ltt_freq_scale_generic(void)
>> +{
>> + return 1;
>> +}
>> +#endif /* _ASM_GENERIC_LTT_H */
>
> --
> Masami Hiramatsu
>
> Software Engineer
> Hitachi Computer Products (America) Inc.
> Software Solutions Division
>
> e-mail: mhiramat at redhat.com
>
>
> _______________________________________________
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> ltt-dev at lists.casi.polymtl.ca
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>
--
Mathieu Desnoyers
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