Re: la la la la ... swappiness

[Andrew Morton <akpm@osdl.org>]

On Tue, 5 Dec 2006 08:17:51 -0800 (PST)
Linus Torvalds <torvalds@osdl.org> wrote:

> 
> 
> On Tue, 5 Dec 2006, Aucoin wrote:
> >
> > > Louis, exactly how do you allocate that big 1.6GB shared area?
> > 
> > Ummm, shm_open, ftruncate, mmap ? Is it a trick question ? The process
> > responsible for initially setting up the shared area doesn't stay resident.
> 
> Not a trick question, I just suddenly realized that I really should have 
> expected the SHM pages to show up in the LRU lists (either inactive or 
> active) and shown up as "cached" pages too. Afaik, the SHM routines all 
> end up using the page cache and the LRU for the backing store.
> 
> But your 1.6GB thing doesn't show up anywhere.
> 
> (I'm sure it's intentional, and I've just forgotten some detail. We 
> probably remove pages from the LRU lists when they are locked. Anyway, my 
> original point was that since the pages _aren't_ on the LRU lists, the VM 
> really should basically act as if they didn't exist at all, but there are 
> probably things that still base their decisions on the _total_ amount of 
> memory)
> 

Yes, those pages should be on the LRU.  I suspect they never got paged in
or something.  But that would mean they weren't mlocked.  Is a mystery.

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