Messages in this thread | | | Date | Wed, 24 Aug 2005 09:08:10 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] blk queue io tracing support |
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On Wed, Aug 24 2005, Nathan Scott wrote: > On Tue, Aug 23, 2005 at 02:32:36PM +0200, Jens Axboe wrote: > > Hi, > > > > This is a little something I have played with. It allows you to see > > exactly what is going on in the block layer for a given queue. Currently > > it can logs request queueing and building, dispatches, requeues, and > > completions. > > Ah, fabulous. Thanks Jens! > > > + t.magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; > > + t.sequence = atomic_add_return(1, &bt->sequence); > > + t.time = sched_clock() / 1000; > > Wouldn't it be better to pass out the highest precision available here > & then do the conversion in userspace instead? I guess one might want > that little bit more for a RAM disk or something ... actually, talking > to one of the SGI people here with alot of experience on IRIX with a > similar facility, the msec resolution there is apparently sometimes an > issue already with fast storage.
This isn't msec precision, it's usec. sched_clock() is in ns! I already decided that msec is too coarse, but usec _should_ be enough.
-- Jens Axboe
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