Re: pre5 VM feedback..

[Marcelo Tosatti]

On 15 Jan 2001, Linus Torvalds wrote:

> In article <[e-mail]>,
> Jeff Garzik  <[e-mail]> wrote:
> >$!@#@! pre6 is already out :)
> 
> Yes, and for heavens sake don't use it, because the reiserfs merge got
> some dirty inode logic wrong. pre7 fixes just that one line and should
> be ok again.
> 
> >Anyway, this may be a totally subjective (and incorrect) perception, but
> >it seems to me like the recent 2.4.x-test kernels and thereafter start
> >swapping things out really quickly.  Case in point:  "diff -urN
> >linux.vanilla linux" command swaps out Konqueror and Netscape Mail, even
> >though I was using them only a few minutes ago.
> 
> Yes. It's really nice for some stuff, but a bit too aggressive for
> normal use, I think.
> 
> If you want to play with tuning, I'd suggest something like
> 
>  - make SWAP_SHIFT bigger (try with 7 instead of 5)
> 
>  - do the "self-swap-out" only for __GFP_VM allocations, and add the
>    __GFP_VM flag to all page fault allocations (ie __GPF_VM would be a
>    flag that says "this allocation will grow my RSS"). 
> 
> The latter is kind of debatable - some allocations can't easily be put
> in one category or the other (ie page cache growing - do we do it
> because of the page cache or because we want to map the page?)

The swapin readahead code tries to allocate (1 << page_cluster) pages at
each swapin. 

This means there's a big chance of having (1 << page_cluster)
"self-swap-out"'s at each swapin if we're under low memory.

Nasty.