Re: excessive swap-in time

On Mon, 17 Mar 2008 01:27:35 +0000 (UTC) Pierre Asselin <pa@xxxxxxxxxxxxxxxxxxxxx> wrote:

| Maybe, maybe not. It could have been swapped out to make room for more
| file cache, inappropriately so --or maybe even appropriately so, it's
| pretty darn hard to guess these things correctly without measuring.

It would be better for the kernel to select pages of other _inactive_
processes when swapping in.


|> The issue is not about
|> the fact that this process is swapped out; it is about doing the swapping
|> in better. Each swapped out page should only need to be swapped back in
|> just once, if this is the only active process.
|
| Maybe that's the issue, then again maybe not. It's not that hard
| to set the swappiness to zero. For what it's worth, that's what
| I do on my laptop while on battery power to better keep the disk
| spun down. If it doesn't help, just restore the default of 60.

I want the processes to swap out. I also want that when they swap back in,
any needs to swap something out to make room should be against other less
active processes.

If swappiness is higher, a copy of the pages should already be in swap space
so stealing a page (from another process, not this active one) should be an
easy steal (nothing dirty, so nothing to write to compete with the swapping
to bring in the active process).

If swappiness is lower or zero, there could be more dirty pages in RAM,
thus making the swap in effort twice as hard since pages to steal need to
be written out.

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