Messages in this thread | | | Date | Thu, 19 Jul 2007 19:24:03 +0200 | From | Jens Axboe <> | Subject | Re: [patch] sched: implement cpu_clock(cpu) high-speed time source, take #2 |
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On Thu, Jul 19 2007, Jeremy Fitzhardinge wrote: > > Index: linux/block/blktrace.c > > =================================================================== > > --- linux.orig/block/blktrace.c > > +++ linux/block/blktrace.c > > @@ -41,7 +41,7 @@ static void trace_note(struct blk_trace > > const int cpu = smp_processor_id(); > > > > t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; > > - t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu); > > + t->time = cpu_clock(cpu) - per_cpu(blk_trace_cpu_offset, cpu); > > t->device = bt->dev; > > t->action = action; > > t->pid = pid; > > @@ -159,7 +159,7 @@ void __blk_add_trace(struct blk_trace *b > > > > t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; > > t->sequence = ++(*sequence); > > - t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu); > > + t->time = cpu_clock(cpu) - per_cpu(blk_trace_cpu_offset, cpu); > > > > What's this measuring here? Time spend in IO? Wouldn't it be better > off with a measurement of real monotonic time?
It's not time spent in IO, it wants a nanosecond timestamp.
-- Jens Axboe
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