svn commit: r219699 - head/sys/kern

[Ivan Voras]

On 16 March 2011 20:59, Garrett Cooper <gcooper at freebsd.org> wrote:
> On Wed, Mar 16, 2011 at 12:51 PM, Ivan Voras <ivoras at freebsd.org> wrote:
>> On 16 March 2011 18:46, Roman Divacky <rdivacky at freebsd.org> wrote:
>>>
>>> On Wed, Mar 16, 2011 at 04:22:59PM +0000, Ivan Voras wrote:
>>> > Author: ivoras
>>> > Date: Wed Mar 16 16:22:59 2011
>>> > New Revision: 219699
>>> > URL: http://svn.freebsd.org/changeset/base/219699
>>> >
>>> > Log:
>>> >   The hardware has caught up; improvements are now observed even at 128,
>>> >   but stay conservative and bump read_max to "only" 64 (it will probably be
>>> >   a good idea to increase this to 128 after the next major release).
>>>
>>> how did you measure this?
>>
>> Specifically for this commit: my desktop 2xSATA 7200 RPM drives,
>> gmirror, single read "dd" stream, bs=1m. (Are there any ready read
>> multi-stream read tests which are not trivial i.e. they start from
>> different positions in the file?)
>
> Would be interesting to see how well things work with the new
> geom_raid bits and with other drives (SAS, SCSI).

Yes, I'd be interested in that; I'll try it when I get the chance to
test new hardware.

For now, there's a report (which actually inspired me to retest and
commit this) from someone who tried this on 2x 15k RPM SAS drives,
with much better results using read_max=128 (thread "gmirror
performance" on freebsd-fs@). I estimate that because his drives were
15kRPM from the start, the improvement isn't as drastic going from 8
to 128 as on these SATA drives I tested on (faster seeks). He went
from ~~ 195 MB/s to ~~ 258 MB/s while I go from ~~ 50 MB/s to ~~ 140
MB/s.