Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev

Vladislav Bolkhovitin
2009-08-03T09:20:08Z

Ronald Moesbergen, on 08/03/2009 01:15 PM wrote:
> 2009/7/31 Vladislav Bolkhovitin <vst@vlnb.net>:
>> OK, as I expected, on the SCST level everything is clear and the forced
>> ordering change didn't change anything.
>>
>> But still, a single read stream must be the fastest from single thread.
>> Otherwise, there's something wrong somewhere in the I/O path: block layer,
>> RA, I/O scheduler. And, apparently, this is what we have and should find out
>> the cause.
>>
>> Can you check if noop on the target and/or initiator makes any difference?
>> Case 5 with 1 and 2 threads will be sufficient.
>
> That doesn't seem to help:
>
> client kernel: 2.6.26-15lenny3 (debian)
> server kernel: 2.6.29.5 with readahead-context, blk_run_backing_dev
> and io_context, forced_order
>
> With one IO thread:
> 5) client: default, server: default (server noop, client noop)
> blocksize R R R R(avg, R(std R
> (bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
> 67108864 17.612 21.113 21.355 51.532 4.680 0.805
> 33554432 18.329 18.523 19.049 54.969 0.891 1.718
> 16777216 18.497 18.219 17.042 57.217 2.059 3.576
>
> With two threads:
> 5) client: default, server: default (server noop, client noop)
> blocksize R R R R(avg, R(std R
> (bytes) (s) (s) (s) MB/s) ,MB/s) (IOPS)
> 67108864 17.436 18.376 20.493 54.807 3.634 0.856
> 33554432 17.466 16.980 18.261 58.337 1.740 1.823
> 16777216 18.222 17.567 18.077 57.045 0.901 3.565

And with client cfq, server noop?

> Ronald.
>