mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 10:49:33 +00:00
perf/x86: Add ability to calculate TSC from perf sample timestamps
For modern CPUs, perf clock is directly related to TSC. TSC can be calculated from perf clock and vice versa using a simple calculation. Two of the three componenets of that calculation are already exported in struct perf_event_mmap_page. This patch exports the third. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: http://lkml.kernel.org/r/1372425741-1676-3-git-send-email-adrian.hunter@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
parent
860f085b74
commit
c73deb6aec
4 changed files with 33 additions and 2 deletions
|
@ -49,6 +49,7 @@ extern void tsc_init(void);
|
|||
extern void mark_tsc_unstable(char *reason);
|
||||
extern int unsynchronized_tsc(void);
|
||||
extern int check_tsc_unstable(void);
|
||||
extern int check_tsc_disabled(void);
|
||||
extern unsigned long native_calibrate_tsc(void);
|
||||
|
||||
extern int tsc_clocksource_reliable;
|
||||
|
|
|
@ -1884,6 +1884,7 @@ static struct pmu pmu = {
|
|||
void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
|
||||
{
|
||||
userpg->cap_usr_time = 0;
|
||||
userpg->cap_usr_time_zero = 0;
|
||||
userpg->cap_usr_rdpmc = x86_pmu.attr_rdpmc;
|
||||
userpg->pmc_width = x86_pmu.cntval_bits;
|
||||
|
||||
|
@ -1897,6 +1898,11 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
|
|||
userpg->time_mult = this_cpu_read(cyc2ns);
|
||||
userpg->time_shift = CYC2NS_SCALE_FACTOR;
|
||||
userpg->time_offset = this_cpu_read(cyc2ns_offset) - now;
|
||||
|
||||
if (sched_clock_stable && !check_tsc_disabled()) {
|
||||
userpg->cap_usr_time_zero = 1;
|
||||
userpg->time_zero = this_cpu_read(cyc2ns_offset);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
|
@ -89,6 +89,12 @@ int check_tsc_unstable(void)
|
|||
}
|
||||
EXPORT_SYMBOL_GPL(check_tsc_unstable);
|
||||
|
||||
int check_tsc_disabled(void)
|
||||
{
|
||||
return tsc_disabled;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(check_tsc_disabled);
|
||||
|
||||
#ifdef CONFIG_X86_TSC
|
||||
int __init notsc_setup(char *str)
|
||||
{
|
||||
|
|
|
@ -378,7 +378,8 @@ struct perf_event_mmap_page {
|
|||
struct {
|
||||
__u64 cap_usr_time : 1,
|
||||
cap_usr_rdpmc : 1,
|
||||
cap_____res : 62;
|
||||
cap_usr_time_zero : 1,
|
||||
cap_____res : 61;
|
||||
};
|
||||
};
|
||||
|
||||
|
@ -420,12 +421,29 @@ struct perf_event_mmap_page {
|
|||
__u16 time_shift;
|
||||
__u32 time_mult;
|
||||
__u64 time_offset;
|
||||
/*
|
||||
* If cap_usr_time_zero, the hardware clock (e.g. TSC) can be calculated
|
||||
* from sample timestamps.
|
||||
*
|
||||
* time = timestamp - time_zero;
|
||||
* quot = time / time_mult;
|
||||
* rem = time % time_mult;
|
||||
* cyc = (quot << time_shift) + (rem << time_shift) / time_mult;
|
||||
*
|
||||
* And vice versa:
|
||||
*
|
||||
* quot = cyc >> time_shift;
|
||||
* rem = cyc & ((1 << time_shift) - 1);
|
||||
* timestamp = time_zero + quot * time_mult +
|
||||
* ((rem * time_mult) >> time_shift);
|
||||
*/
|
||||
__u64 time_zero;
|
||||
|
||||
/*
|
||||
* Hole for extension of the self monitor capabilities
|
||||
*/
|
||||
|
||||
__u64 __reserved[120]; /* align to 1k */
|
||||
__u64 __reserved[119]; /* align to 1k */
|
||||
|
||||
/*
|
||||
* Control data for the mmap() data buffer.
|
||||
|
|
Loading…
Reference in a new issue