anticipatory scheduling questions

Felipe Alfaro Solana (felipe_alfaro@linuxmail.org)
Thu, 27 Feb 2003 23:24:40 +0100

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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