Messages in this thread |  | | Date | Wed, 24 Jan 2001 02:27:26 +0100 | From | Andrea Arcangeli <> |
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On Wed, Jan 24, 2001 at 01:43:26AM +0100, Sasi Peter wrote: > (30+ high speed streams from 4 disks does really need some caching).
This isn't obvious. Your working may not fit in cache and so the kernel understand it's worthless to swapout stuff to make space to a polluted cache.
> Can't say, of these many daemons nothing can be swapped out (and should > under I/O load)!
If you run `cp /dev/zero .` on a smart VM nothing must be swapped out even if it generated nearly the maximal I/O flood possible. It's worthless to let a polluted cache to grow. It won't help anyways and you'll run slower the next time you'll have to pagein from swap.
It _enterely_ depends on the I/O load pattern if it worth to swapout or not to make space for filesystem cache.
> The performance just used to be better, but the whole more instable. > > Be this, if this is the price for stability.
As said we can add bits of page aging (that can't destabilize anything and it will only affect performance behaviour), but I'd prefer to be sure you really get a slowdown due the new VM behaviour (because more aging if done without multiqueue O(1) approch can introduces waste of CPU and cachelines in kernel space), so could you try to kill notes and squid and the other unused stuff and to see if you return to deliver performance as with the older kernels? I still miss this important information (last thing you said me was that with 100mbyte in cache it swapouts, and without knowing the details of the I/O pattern it looked sane). After that I'd also like to know what happens with 2.4.0 that uses multiqueue and that is also able to detect pollution and to avoid swapping out in such case.
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