On Thu, 11 Sep 2008, Scott Carey wrote:
Preliminary summary:

readahead  |  8 conc read rate  |  1 conc read rate
49152  |  311  |  314
16384  |  312  |  312
12288  |  304  |  309
 8192  |  292  |
 4096  |  264  |
 2048  |  211  |
 1024  |  162  |  302
  512  |  108  |
  256  |  81  | 300
    8  |  38  |

What io scheduler are you using? The anticipatory scheduler is meant to prevent this slowdown with multiple concurrent reads.

Matthew


--
And the lexer will say "Oh look, there's a null string. Oooh, there's another. And another.", and will fall over spectacularly when it realises
there are actually rather a lot.
        - Computer Science Lecturer (edited)
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