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| author | David Rientjes <rientjes@google.com> | 2009-07-07 00:14:14 -0700 |
|---|---|---|
| committer | Pekka Enberg <penberg@cs.helsinki.fi> | 2009-07-10 09:52:55 +0300 |
| commit | fa5ec8a1f66f3c2a3af723abcf8085509c9ee682 (patch) | |
| tree | be8e06f8ace38ed40ec2af4465dd1fffbc4b4f09 /Documentation/vm/slub.txt | |
| parent | c2cc49a2f8a479dde96a599646d30b6cc9dbed78 (diff) | |
| download | linux-fa5ec8a1f66f3c2a3af723abcf8085509c9ee682.tar.gz linux-fa5ec8a1f66f3c2a3af723abcf8085509c9ee682.tar.bz2 linux-fa5ec8a1f66f3c2a3af723abcf8085509c9ee682.zip | |
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>
Diffstat (limited to 'Documentation/vm/slub.txt')
| -rw-r--r-- | Documentation/vm/slub.txt | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index bb1f5c6e28b3..510917ff59ed 100644 --- a/Documentation/vm/slub.txt +++ b/Documentation/vm/slub.txt @@ -41,6 +41,8 @@ Possible debug options are P Poisoning (object and padding) U User tracking (free and alloc) T Trace (please only use on single slabs) + O Switch debugging off for caches that would have + caused higher minimum slab orders - Switch all debugging off (useful if the kernel is configured with CONFIG_SLUB_DEBUG_ON) @@ -59,6 +61,14 @@ to the dentry cache with slub_debug=F,dentry +Debugging options may require the minimum possible slab order to increase as +a result of storing the metadata (for example, caches with PAGE_SIZE object +sizes). This has a higher liklihood of resulting in slab allocation errors +in low memory situations or if there's high fragmentation of memory. To +switch off debugging for such caches by default, use + + slub_debug=O + In case you forgot to enable debugging on the kernel command line: It is possible to enable debugging manually when the kernel is up. Look at the contents of: |