lkml.org 
[lkml]   [2003]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest]
Andrew Morton wrote:

>Nick Piggin <piggin@cyberone.com.au> wrote:
>
>>That is what I can't understand. Movement of the disk head should
>>be exactly the same in either situation and 128K is not exactly
>>a pitiful request size - so it suggests a quirk somewhere. It
>>is not as if the disk has to be particularly smart or know a
>>lot about the data in order to optimise the head movement for
>>a load like this.
>>
>
>Yes, that's a bit odd. Some reduction in CPU cost and bus
>traffic, etc would be expected. Could be that sending out a
>request which is larger than a track is saving a rev of the disk
>for some reason.
>
Shouldn't be. Even at 128KB readahead we should always have
outstanding requests against the disk in a streaming read
scenario, right? Maybe if the track buffers are bigger than
128K?

Is there a magic number above which you see the improvement,
Andrea? Or does it steadily climb?

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:33    [from the cache]
©2003-2011 Jasper Spaans