Re: [PATCH] mm, slub: Consider rest of partial list if acquire_slab() fails

[David Rientjes]

On Mon, 28 Dec 2020, Jann Horn wrote:

> acquire_slab() fails if there is contention on the freelist of the page
> (probably because some other CPU is concurrently freeing an object from the
> page). In that case, it might make sense to look for a different page
> (since there might be more remote frees to the page from other CPUs, and we
> don't want contention on struct page).
> 
> However, the current code accidentally stops looking at the partial list
> completely in that case. Especially on kernels without CONFIG_NUMA set,
> this means that get_partial() fails and new_slab_objects() falls back to
> new_slab(), allocating new pages. This could lead to an unnecessary
> increase in memory fragmentation.
> 
> Fixes: 7ced37197196 ("slub: Acquire_slab() avoid loop")
> Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>

Indeed, it looks like commit 7ced37197196 ("slub: Acquire_slab() avoid 
loop") stopped the iteration prematurely.