Hi,

I did something similiar in the patch I posted under the subject:

[RFC][PATCH] cache shrinking via page age

Only I used the same method we now use to shrink caches but triggered them
using page aging, and at the same time making the trigger cache specific.

Another though I had was to put the 'freeable' slab pages onto the inactive
clean list and reclaim them when they reach the head of the list.  It gets a 
little tricky since slabs can contain multiple pages...   Before trying this
I want to see how well what I have posted works.

Ed Tomlinson

On May 13, 2002 07:07 am, Nikita Danilov wrote:

William Lee Irwin III writes:
 > At some point in the past, I wrote:
 > >> In short, I don't think you went far enough. How do you feel about
 > >> GFP_SPECULATIVE (a.k.a. GFP_DONT_TRY_TOO_HARD), cache priorities and
 > >> cache shrinking drivers?
 >
 > On Tue, May 07, 2002 at 07:41:52AM -0400, Ed Tomlinson wrote:
 > > Think I will sprinkle slab.c with a printk or two to see if we detect
 > > when it's allocations are eating other caches.  If this works we
 > > should be able to let the vm know when to shrink the slab cache and to
 > > let it know which caches need shrinking (ie shrink_caches becomes a
 > > 'driver' to shrink the dcache/icache family.  kmem_cache_reap being
 > > the generic 'driver') Thanks for the feedback and interesting idea,
 >
 > Well, the trick is kmem_cache_reap() doesn't know how to prune
 > references to things within the cache like prune_dcache() does. It is
 > in essence its own cache in front of another cache for allocations. I'm
 > not sure making kmem_cache_reap() trigger reaping of the caches it's
 > parked in front of is a great idea. It seems that it would go the other
 > direction: reaping a cache parked in front of a slab would want to call
 > kmem_cache_reap() sometime afterward (so the memory is actually
 > reclaimed instead of sitting in the slab cache). IIRC the VM actually
 > does this at some point after calling the assorted cache shrink
 > functions. kmem_cache_reap() may well be needed in contexts where the
 > caches are doing fine jobs of keeping their space under control or
 > shrinking themselves just fine, without intervention from outside
 > callers.

I remember Linus once mentioned an idea that slab pages should have
->writepage() that triggers shrink of the front-end cache.

Along this way, VM would just manage one big cache---physical memory.

 > Cheers,
 > Bill

Nikita.

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