Messages in this thread | | | Date | Mon, 3 Jul 2006 23:42:17 +0200 | Subject | Re: New readahead - ups and downs new test. Vm oddities. | From | Helge Hafting <> |
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I have now re-run my tests (parallel debsums and bzcat+patch) this time with everything on the same device so as to get competition for io.
New and old readahead didn't make much difference this time either, so it seems that my idea about readahead problems were wrong. Which is good, as the new readahead improves so many other things.
Results with new readahead using one disk device: Swap went up to 32M, dropped to 244k when testing ended. patch timing: real 6m8.451s user 0m5.183s sys 0m2.897s debsums timing: real 7m42.851s user 0m21.172s sys 0m13.642s
Results with old readahead, one disk device: Swap went to 32M, dropped to 244k when testing ended. timings: patch: real 6m18.191s user 0m5.226s sys 0m2.724s debsums: real 7m49.860s user 0m21.243s sys 0m14.268s A tiny bit slower, but very little.
No surprise that everyting is slower when using a single disk instead of two.
The swap difference from using two disks is striking though. Nothing to do with readahead, but why 32M swap when using one disk, and 244k swap when using two?
The amount of data processed is the same either way, is the VM very timing-sensitive?
Helge Hafting
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