Re: [PATCH] 2.3.99-pre6-3+ VM rebalancing

["Stephen C. Tweedie" <sct@redhat.com>]

Hi,

On Wed, Apr 26, 2000 at 08:15:14AM -0300, Rik van Riel wrote:
> On Wed, 26 Apr 2000, Stephen C. Tweedie wrote:
> > On Tue, Apr 25, 2000 at 12:06:58PM -0700, Simon Kirby wrote:
> > > 
> > > Sorry, I made a mistake there while writing..I was going to give an
> > > example and wrote 60 seconds, but I didn't actually mean to limit
> > > anything to 60 seconds.  I just meant to make a really big global lru
> > > that contains everything including page cache and swap. :)
> > 
> > Doesn't work.  If you do that, a "find / | grep ..." swaps out 
> > everything in your entire system.
> > 
> > Getting the VM to respond properly in a way which doesn't freak out
> > in the mass-filescan case is non-trivial.  Simple LRU over all pages
> > simply doesn't cut it.
> 
> It seems to work pretty well, because pages "belonging to" processes
> are mapped into the address space of each process and will never go
> through swap_out() if shrink_mmap() will succeed.

I know.  The post wasn't talking about what we do now.  It was talking
about a hypothetical LRU which covers "everything including page cache
and swap."  LRU over just the page cache pages works fine.  If you 
start treating swap exactly the same, on a page-by-page LRU, then a
filesystem "find" scan will swap out most of your VM.  Bad news.

--Stephen
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