Re: New patch (was Re: [PATCH] swapin readahead v3 + kswapd fixes)

[Rik van Riel <H.H.vanRiel@phys.uu.nl>]

On Tue, 22 Dec 1998, Andrea Arcangeli wrote:
> On 22 Dec 1998, Eric W. Biederman wrote:
> 
> >My suggestion (again) would be to not call shrink_mmap in the swapper
> >(unless we are endangering atomic allocations).  And to never call
> >swap_out in the memory allocator (just wake up kswapd).
> 
> Ah, I just had your _same_ _exactly_ idea yesterday but there' s a
> good reason I nor proposed/tried it. The point are Real time
> tasks. kswapd is not realtime and a realtime task must be able to
> swapout a little by itself in try_to_free_pages() when there's
> nothing to free on the cache anymore.

- kswapd should make sure that there is enough on the cache
  (we should keep track of how many 1-count cache pages there
  are in the system)
- realtime tasks shouldn't go around allocating huge amounts
  of memory -- this totally ruins the realtime aspect anyway

> (and this will avoid also tasks other than kswapd to
> sleep waiting for slowww SYNC IO). 

Some tasks (really big memory hogs) are better left sleeping
for I/O because they otherwise completely overpower the rest
of the system. But that's a slightly different story :)

cheers,

Rik -- the flu hits, the flu hits, the flu hits -- MORE
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| Linux memory management tour guide.        H.H.vanRiel@phys.uu.nl |
| Scouting Vries cubscout leader.      http://www.phys.uu.nl/~riel/ |
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