On Tue, 2004-08-24 at 23:17, K.R. Foley wrote:/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.
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