Re: [PATCH 3/3] mm: slub: Default slub_max_order to 0

Andrew Morton
2011-05-12T17:30:34Z

On Thu, 12 May 2011 18:10:38 +0200 Eric Dumazet <eric.dumazet@gmail.com> wrote:

> More fuel to this discussion with commit 6d4831c2
>
> Something is wrong with high order allocations, on some machines.
>
> Maybe we can find real cause instead of limiting us to use order-0 pages
> in the end... ;)
>
> commit 6d4831c283530a5f2c6bd8172c13efa236eb149d
> Author: Andrew Morton <akpm@linux-foundation.org>
> Date: Wed Apr 27 15:26:41 2011 -0700
>
> vfs: avoid large kmalloc()s for the fdtable

Well, it's always been the case that satisfying higher-order
allocations take a disproportionate amount of work in page reclaim.
And often causes excessive reclaim.

That's why we've traditionally worked to avoid higher-order
allocations, and this has always been a problem with slub.

But the higher-order allocations shouldn't cause the VM to melt down.
We changed something, and now it melts down. Changing slub to avoid
that meltdown doesn't fix the thing we broke.