Re: [PATCH -mm 1/3] slub: don't fail kmem_cache_shrink if slab placement optimization fails

[Christoph Lameter <cl@linux.com>]

On Mon, 26 Jan 2015, Vladimir Davydov wrote:

> Anyways, I think that silently relying on the fact that the allocator
> never fails small allocations is kind of unreliable. What if this

We are not doing that though. If the allocation fails we do nothing.

> > > +			if (page->inuse < objects)
> > > +				list_move(&page->lru,
> > > +					  slabs_by_inuse + page->inuse);
> > >  			if (!page->inuse)
> > >  				n->nr_partial--;
> > >  		}
> >
> > The condition is always true. A page that has page->inuse == objects
> > would not be on the partial list.
> >
>
> This is in case we failed to allocate the slabs_by_inuse array. We only
> have a list for empty slabs then (on stack).

Ok in that case objects == 1. If you want to do this maybe do it in a more
general way?

You could allocate an array on the stack to deal with the common cases. I
believe an array of 32 objects would be fine to allocate and cover most of
the slab caches on the system? Would eliminate most of the allocations in
kmem_cache_shrink.