anticipatory scheduling questions

["Felipe Alfaro Solana" <felipe_alfaro@linuxmail.org>]

Hello, 
 
I have just installed 2.5.63-mm1 on my system and have been performing a very simple benchmarks. Here are 
my first results when compared against a RedHat 2.4.20-2.54 kernel: 
 
(All times expressed as total times) 
 
1. time dd if=/dev/zero of=/tmp/p bs=1024k count=256 
2.5.63-mm1 -> 0m12.737s 
2.4.20-2.54 -> 0m17.704s 
 
2. time cp /tmp/p /tmp/q 
2.5.63-mm1 -> 0m41.108s 
2.4.20-2.54 -> 0m51.939s 
 
3. time cmp /tmp/p /tmp/q 
2.5.63-mm1 -> 1m7.349s 
2.4.20-2.54 -> 0m58.966s 
 
4. time cmp /dev/zero /tmp/q 
2.5.63-mm1 -> 0m17.965s 
2.4.20-2.54 -> 0m14.038s 
 
The question is, why, apparently, is anticipatory scheduling perfomring worse than 2.4.20? Indeed, this can be 
tested interactively with an application like Evolution: I have configured Evolution to use 2 dictionaries (English 
and Spanish) for spell checking in e-mail messages. When running 2.4.20, if I choose to reply to a large 
message, it only takes a few seconds to read both dictionaries from disk and perform the spell checking. 
However, on 2.5.63-mm1 the same process takes considerably longer. Any reason for this? 
 
Thanks! 
 
Best regards, 
 
   Felipe Alfaro Solana 
 
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