Messages in this thread | | | Subject | Re: Higher than expected disk write(2) latency | From | Chris Mason <> | Date | Thu, 10 Jul 2008 10:18:32 -0400 |
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On Thu, 2008-07-10 at 07:01 -0700, Arjan van de Ven wrote: > On Thu, 10 Jul 2008 15:41:46 +0200 > Martin Lucina <mato@kotelna.sk> wrote: > > > chris.mason@oracle.com said: > > > Is NCQ enabled on the drive? The basic way to fix this is to have > > > multiple requests in flight, which isn't going to happen on sata > > > with the cache off and with ncq off. > > > > ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300) > > ata1.00: ATA-7: Hitachi HDS721616PLA380, P22OAB3A, max UDMA/133 > > ata1.00: 321672960 sectors, multi 0: LBA48 NCQ (depth 31/32) > > ata1.00: configured for UDMA/133 > > > > I'm assuming the above indicates NCQ is enabled. > > > > We'll try running the tests tomorrow with different i/o schedulers and > > report back. > > > another thing to try is using AHCI mode instead; AHCI tends to be > higher performance > > (and.. for fun try to run latencytop during a run, to see if maybe > there are unsuspected delay causes) > Any latencies during submit (at least for kernel aio) are probably from get_request_wait, but the numbers so far look like they are only seeing one request in flight at a time.
-chris
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