Re: Slow perfs with IDE SSD

[Tejun Heo <htejun@gmail.com>]

Tejun Heo wrote:
> François-Julien Marbaud wrote:
>> Hi !
>>
>> I'm doing an internship in a research lab, and we are trying to use a 
>> P.ATA SSD
>> in order to speed-up a genome computation software.
>>
>> We got a performance problem, expecially with access time : access 
>> time is about
>> 800us, and according to the manufacturer it should be about 40us. The 
>> bandwith
>> is OK.
>>
>> The SSD is a 2.5' flash hard drive, the slave of the first IDE channel.
>>
>> We wonder if that could be the because P.ATA driver is not really done 
>> for small
>> access times, so we got such a poor time. In that case, I guess we 
>> would have to
>> have a closer look at the driver ... 
> 
> First of all, try noop elevator.
> 
>   echo noop > /sys/block/hdx/queue/scheduler
> 
> Depending on your workload, adjusting plugging delay/threshold 
> parameters might help.  These are initialized in the kernel source file 
> block/ll_rw_blk.c::blk_queue_make_request().  q->unplug_thresh and 
> q->unplug_delay.
> 

And one more thing, if a 67MB~4GB SDD drive speeds up the computation, 
something is wrong.  4GB main memory will be much better than 4GB SDD 
for such purposes.

-- 
tejun