On Thu, 8 Nov 2012 17:15:36 +0000 Christoph Lameter <cl@xxxxxxxxx> wrote: > On Wed, 7 Nov 2012, Andrew Morton wrote: > > > What's up with kmem_cache_shrink? It's global and exported to modules > > but its only external caller is some weird and hopelessly poorly > > documented site down in drivers/acpi/osl.c. slab and slob implement > > kmem_cache_shrink() *only* for acpi! wtf? Let's work out what acpi is > > trying to actually do there, then do it properly, then killkillkill! > > kmem_cache_shrink is also used internally. Its simply releasing unused > cached objects. Only in slub. It could be removed outright from the others and simplified in slub. > > Secondly, as slab and slub (at least) have the ability to shed cached > > memory, why aren't they hooked into the core cache-shinking machinery. > > After all, it's called "shrink_slab"! > > Because the core cache shrinking needs the slab caches to free up memory > from inodes and dentries. We could call kmem_cache_shrink at the end of > the shrink passes in vmscan. The price would be that the caches would have > to be repopulated when new allocations occur. Well, the shrinker shouldn't strips away all the cache. It will perform a partial trim, the magnitude of which increases with perceived external memory pressure. AFACIT, this is correct and desirable behaviour for shrinking slab's internal caches. > > > > If we can fix all that up then I wonder whether this particular patch > > needs to exist at all. If the kmem_cache is no longer used then we > > can simply leave it floating around in memory and the regular cache > > shrinking code out of shrink_slab() will clean up any remaining pages. > > The kmem_cache itself can be reclaimed via another shrinker, if > > necessary? > > The kmem_cache can only be released if all its objects (used and unused) > are released. kmem_cache_shrink drops the unused objects on some internal > slab specific list. That may enable us to release the kmem_cache > structure. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>