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On Tue, Mar 14 2006, Lee Revell wrote: > On Tue, 2006-03-14 at 07:40 +0100, Mike Galbraith wrote: > > On Sat, 2006-03-11 at 23:54 -0500, Lee Revell wrote: > > > On Sat, 2006-03-11 at 08:51 +0100, Mike Galbraith wrote: > > > > There used to be a pages in flight 'restrictor plate' in there that > > > > would have probably helped this situation at least a little. But in > > > > any case, it sounds like you'll have to find a way to submit the IO in > > > > itty bitty synchronous pieces. > > > > > > echo 64 > /sys/block/hd*/queue/max_sectors_kb > > > > > > There is basically a straight linear relation between whatever you set > > > this to and the maximum scheduling latency you see. It was developed to > > > solve the exact problem you are describing. > > > > <head-scratching> > > > > Is it possible that you mean pci latency? I'm unable to measure any > > scheduling latency > 5ms while pushing IO for all my little Barracuda > > disk is worth. > > It's only a big problem if LBA48 is in use which allows 32MB of IO to be > in flight at once, this depends on the size of the drive. > > What does that value default to? Not quite true. Even if lba48 is active on the drive, we don't allow more than 1MB per request. And nit picking a little, lba48 doesn't always depend on the size of the drive, some drives smaller than 2^28 sectors also feature lba48 support. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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