Shachar f, on 11/25/2009 07:57 PM wrote:
> I'm running open-iscsi with scst on Broadcom 10Gig network and facing 
> write latency issues.
> When using netperf over an idle network the latency for a single block 
> round trip transfer is 30 usec and with open-iscsi it is 90-100 usec.
>  
> I see that Nagle (TCP_NODELAY) is disabled when openning socket on the 
> initiator side and I'm not sure about the target side. 
> Vlad, Can you elaborate on this?

TCP_NODELAY is always enabled in iSCSI-SCST. You can at any time have 
latency statistics on the target side by enabling 
CONFIG_SCST_MEASURE_LATENCY (see README). Better also enable 
CONFIG_PREEMPT_NONE to not count CPU scheduler latency.

> Are others in the mailing list aware to possible environment changes 
> that effext latency?
>  
> more info -
> I'm running this test with Centos5.3 machines with almost latest open-iscsi.
>  
> Thanks,
>   Shachar

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