tree be8e06f8ace38ed40ec2af4465dd1fffbc4b4f09
parent c2cc49a2f8a479dde96a599646d30b6cc9dbed78
author David Rientjes <rientjes@google.com> 1246950854 -0700
committer Pekka Enberg <penberg@cs.helsinki.fi> 1247208775 +0300

slub: add option to disable higher order debugging slabs

When debugging is enabled, slub requires that additional metadata be
stored in slabs for certain options: SLAB_RED_ZONE, SLAB_POISON, and
SLAB_STORE_USER.

Consequently, it may require that the minimum possible slab order needed
to allocate a single object be greater when using these options.  The
most notable example is for objects that are PAGE_SIZE bytes in size.

Higher minimum slab orders may cause page allocation failures when oom or
under heavy fragmentation.

This patch adds a new slub_debug option, which disables debugging by
default for caches that would have resulted in higher minimum orders:

	slub_debug=O

When this option is used on systems with 4K pages, kmalloc-4096, for
example, will not have debugging enabled by default even if
CONFIG_SLUB_DEBUG_ON is defined because it would have resulted in a
order-1 minimum slab order.

Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>