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| author | Peter Zijlstra <peterz@infradead.org> | 2013-11-29 15:40:29 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2014-01-13 15:13:06 +0100 |
| commit | 20d1c86a57762f0a33a78988e3fc8818316badd4 (patch) | |
| tree | c200d1bf1394460a1c3b1cfb790773f8377543ba /arch/x86/kernel/cpu/perf_event.c | |
| parent | 57c67da274f3fab38e08d2c9edf08b89e1d9c71d (diff) | |
| download | linux-20d1c86a57762f0a33a78988e3fc8818316badd4.tar.gz linux-20d1c86a57762f0a33a78988e3fc8818316badd4.tar.bz2 linux-20d1c86a57762f0a33a78988e3fc8818316badd4.zip | |
sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs
Use a ring-buffer like multi-version object structure which allows
always having a coherent object; we use this to avoid having to
disable IRQs while reading sched_clock() and avoids a problem when
getting an NMI while changing the cyc2ns data.
MAINLINE PRE POST
sched_clock_stable: 1 1 1
(cold) sched_clock: 329841 331312 257223
(cold) local_clock: 301773 310296 309889
(warm) sched_clock: 38375 38247 25280
(warm) local_clock: 100371 102713 85268
(warm) rdtsc: 27340 27289 24247
sched_clock_stable: 0 0 0
(cold) sched_clock: 382634 372706 301224
(cold) local_clock: 396890 399275 399870
(warm) sched_clock: 38194 38124 25630
(warm) local_clock: 143452 148698 129629
(warm) rdtsc: 27345 27365 24307
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-s567in1e5ekq2nlyhn8f987r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu/perf_event.c')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 8e132931614d..9f97bd03f74f 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -1883,6 +1883,8 @@ static struct pmu pmu = { void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) { + struct cyc2ns_data *data; + userpg->cap_user_time = 0; userpg->cap_user_time_zero = 0; userpg->cap_user_rdpmc = x86_pmu.attr_rdpmc; @@ -1891,13 +1893,17 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) if (!sched_clock_stable) return; + data = cyc2ns_read_begin(); + userpg->cap_user_time = 1; - userpg->time_mult = this_cpu_read(cyc2ns); - userpg->time_shift = CYC2NS_SCALE_FACTOR; - userpg->time_offset = this_cpu_read(cyc2ns_offset) - now; + userpg->time_mult = data->cyc2ns_mul; + userpg->time_shift = data->cyc2ns_shift; + userpg->time_offset = data->cyc2ns_offset - now; userpg->cap_user_time_zero = 1; - userpg->time_zero = this_cpu_read(cyc2ns_offset); + userpg->time_zero = data->cyc2ns_offset; + + cyc2ns_read_end(data); } /* |