aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/posix-timers.c
diff options
context:
space:
mode:
authorjohn stultz <johnstul@us.ibm.com>2009-08-19 22:13:34 -0400
committerThomas Gleixner <tglx@linutronix.de>2009-08-21 15:43:46 -0400
commitda15cfdae03351c689736f8d142618592e3cebc3 (patch)
tree497fe3f77e27fa9cf0a484422c7bc382031df1bd /kernel/posix-timers.c
parent8cab02dc3c58a12235c6d463ce684dded9696848 (diff)
time: Introduce CLOCK_REALTIME_COARSE
After talking with some application writers who want very fast, but not fine-grained timestamps, I decided to try to implement new clock_ids to clock_gettime(): CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE which returns the time at the last tick. This is very fast as we don't have to access any hardware (which can be very painful if you're using something like the acpi_pm clocksource), and we can even use the vdso clock_gettime() method to avoid the syscall. The only trade off is you only get low-res tick grained time resolution. This isn't a new idea, I know Ingo has a patch in the -rt tree that made the vsyscall gettimeofday() return coarse grained time when the vsyscall64 sysctrl was set to 2. However this affects all applications on a system. With this method, applications can choose the proper speed/granularity trade-off for themselves. Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: nikolag@ca.ibm.com Cc: Darren Hart <dvhltc@us.ibm.com> Cc: arjan@infradead.org Cc: jonathan@jonmasters.org LKML-Reference: <1250734414.6897.5.camel@localhost.localdomain> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/posix-timers.c')
-rw-r--r--kernel/posix-timers.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index d089d052c4a9..495440779ce3 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -242,6 +242,25 @@ static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec *tp)
242 return 0; 242 return 0;
243} 243}
244 244
245
246static int posix_get_realtime_coarse(clockid_t which_clock, struct timespec *tp)
247{
248 *tp = current_kernel_time();
249 return 0;
250}
251
252static int posix_get_monotonic_coarse(clockid_t which_clock,
253 struct timespec *tp)
254{
255 *tp = get_monotonic_coarse();
256 return 0;
257}
258
259int posix_get_coarse_res(const clockid_t which_clock, struct timespec *tp)
260{
261 *tp = ktime_to_timespec(KTIME_LOW_RES);
262 return 0;
263}
245/* 264/*
246 * Initialize everything, well, just everything in Posix clocks/timers ;) 265 * Initialize everything, well, just everything in Posix clocks/timers ;)
247 */ 266 */
@@ -262,10 +281,26 @@ static __init int init_posix_timers(void)
262 .timer_create = no_timer_create, 281 .timer_create = no_timer_create,
263 .nsleep = no_nsleep, 282 .nsleep = no_nsleep,
264 }; 283 };
284 struct k_clock clock_realtime_coarse = {
285 .clock_getres = posix_get_coarse_res,
286 .clock_get = posix_get_realtime_coarse,
287 .clock_set = do_posix_clock_nosettime,
288 .timer_create = no_timer_create,
289 .nsleep = no_nsleep,
290 };
291 struct k_clock clock_monotonic_coarse = {
292 .clock_getres = posix_get_coarse_res,
293 .clock_get = posix_get_monotonic_coarse,
294 .clock_set = do_posix_clock_nosettime,
295 .timer_create = no_timer_create,
296 .nsleep = no_nsleep,
297 };
265 298
266 register_posix_clock(CLOCK_REALTIME, &clock_realtime); 299 register_posix_clock(CLOCK_REALTIME, &clock_realtime);
267 register_posix_clock(CLOCK_MONOTONIC, &clock_monotonic); 300 register_posix_clock(CLOCK_MONOTONIC, &clock_monotonic);
268 register_posix_clock(CLOCK_MONOTONIC_RAW, &clock_monotonic_raw); 301 register_posix_clock(CLOCK_MONOTONIC_RAW, &clock_monotonic_raw);
302 register_posix_clock(CLOCK_REALTIME_COARSE, &clock_realtime_coarse);
303 register_posix_clock(CLOCK_MONOTONIC_COARSE, &clock_monotonic_coarse);
269 304
270 posix_timers_cache = kmem_cache_create("posix_timers_cache", 305 posix_timers_cache = kmem_cache_create("posix_timers_cache",
271 sizeof (struct k_itimer), 0, SLAB_PANIC, 306 sizeof (struct k_itimer), 0, SLAB_PANIC,