diff options
author | Ingo Molnar <mingo@elte.hu> | 2007-07-09 16:51:58 (GMT) |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2007-07-09 16:51:58 (GMT) |
commit | 20d315d42aed95423a7203e1d7e84086004b5a00 (patch) | |
tree | 3649d00c3ed1053783727333de1291a71bdb3ca4 /kernel | |
parent | 6aa645ea5f7a246702e07f29edc7075d487ae4a3 (diff) | |
download | linux-20d315d42aed95423a7203e1d7e84086004b5a00.tar.xz |
sched: add rq_clock()/__rq_clock()
add rq_clock()/__rq_clock(), a robust wrapper around sched_clock(),
used by CFS. It protects against common type of sched_clock() problems
(caused by hardware): time warps forwards and backwards.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched.c | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 085418b..29eb227 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -389,6 +389,52 @@ static inline int cpu_of(struct rq *rq) } /* + * Per-runqueue clock, as finegrained as the platform can give us: + */ +static unsigned long long __rq_clock(struct rq *rq) +{ + u64 prev_raw = rq->prev_clock_raw; + u64 now = sched_clock(); + s64 delta = now - prev_raw; + u64 clock = rq->clock; + + /* + * Protect against sched_clock() occasionally going backwards: + */ + if (unlikely(delta < 0)) { + clock++; + rq->clock_warps++; + } else { + /* + * Catch too large forward jumps too: + */ + if (unlikely(delta > 2*TICK_NSEC)) { + clock++; + rq->clock_overflows++; + } else { + if (unlikely(delta > rq->clock_max_delta)) + rq->clock_max_delta = delta; + clock += delta; + } + } + + rq->prev_clock_raw = now; + rq->clock = clock; + + return clock; +} + +static inline unsigned long long rq_clock(struct rq *rq) +{ + int this_cpu = smp_processor_id(); + + if (this_cpu == cpu_of(rq)) + return __rq_clock(rq); + + return rq->clock; +} + +/* * The domain tree (rq->sd) is protected by RCU's quiescent state transition. * See detach_destroy_domains: synchronize_sched for details. * |