Messages in this thread | | | Date | Wed, 5 Dec 2001 19:20:55 +0100 (CET) | From | Roy Sigurd Karlsbakk <> | Subject | Re: /proc/sys/vm/(max|min)-readahead effect???? |
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> > I've got a lot of memory (some 380 megs), but what is VM pressure? > > VM pressure means that there is not enough free memory on the system... > Allocators have to reclaim memory.
There's more than enough memory on the system, as far as I can see
[root@linuxserver ext2]# free total used free shared buffers cached Mem: 381500 378136 3364 0 3552 333348 -/+ buffers/cache: 41236 340264 Swap: 522104 11440 510664
> Basically you cannot simply expect an increase in readahead size to > increase performance: > > 1) The files you created may not be sequential
Beleive me - they are! Created with 'dd' secuentially
> 2) The lack of memory on the system may be interfering in weird ways, and > maybe _INCREASING_ the readahead may decrease performance.
Anyway - I beleive I should have seen some change by trying virtually any value from 31 to 4095.
If the readahead is what I beleive it is, It'll read further out in the file when a request comes. It looks like either this never happens, or the next request doesn't 'know' how much is cached.
roy
-- Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA
Computers are like air conditioners. They stop working when you open Windows.
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