Messages in this thread |  | | | Date | Wed, 25 Aug 2004 09:34:39 -0500 | | From | "K.R. Foley" <> | | Subject | Re: [patch] voluntary-preempt-2.6.8.1-P9 |
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Lee Revell wrote: > On Tue, 2004-08-24 at 23:17, K.R. Foley wrote: > >>Ingo Molnar wrote: >> >>> http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.8.1-P9 >>> > > >>latency trace of ~148 usec in scsi_request? I don't know if this is real >>or not. Note the 79 usec here: >> >>00000001 0.107ms (+0.079ms): sd_init_command (scsi_prep_fn) >> >>Entire trace is here: >> >>http://www.cybsft.com/testresults/2.6.8.1-P9/latency_trace7.txt >> >> >>Is this possible? This is not the first time I have seen this. There is >>another one here: >> >>http://www.cybsft.com/testresults/2.6.8.1-P9/latency_trace5.txt >> > > > This looks like a real latency. What is > /sys/block/sdX/queue/max_sectors_kb set to? Does lowering it help? > > Lee > > /sys/block/sda/queue/max_sectors_kb was set to 512, trying it at 256. Hard to say whether it is helping or not. Looking at dmesg I do see some traces for scsi_request in the range of 39 - 72 usec. However, anything higher (up to 115 usec) could be masked by one of the netif_skb latencies that I am still seeing. Not only that, but I have only caught a hand-full of these scsi traces in all of my testing.
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