anticipatory scheduling questions

From: Felipe Alfaro Solana (felipe_alfaro@linuxmail.org)
Date: Thu Feb 27 2003 - 17:24:40 EST


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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