driver-core: fix devtmpfs crash on s390

[safe/jmp/linux-2.6] / Documentation / vm / slub.txt

diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt
index dcf8bcf..b37300e 100644 (file)
--- 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)
 
@@ -50,14 +52,22 @@ F.e. in order to boot just with sanity checks and red zoning one would specify:
 
 Trying to find an issue in the dentry cache? Try
 
-       slub_debug=,dentry_cache
+       slub_debug=,dentry
 
 to only enable debugging on the dentry cache.
 
 Red zoning and tracking may realign the slab.  We can just apply sanity checks
 to the dentry cache with
 
-       slub_debug=F,dentry_cache
+       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
@@ -235,7 +245,7 @@ been overwritten. Here a string of 8 characters was written into a slab that
 has the length of 8 characters. However, a 8 character string needs a
 terminating 0. That zero has overwritten the first byte of the Redzone field.
 After reporting the details of the issue encountered the FIX SLUB message
-tell us that SLUB has restored the Redzone to its proper value and then
+tells us that SLUB has restored the Redzone to its proper value and then
 system operations continue.
 
 Emergency operations:
@@ -266,4 +276,4 @@ of other objects.
 
        slub_debug=FZ,dentry
 
-Christoph Lameter, <clameter@sgi.com>, May 30, 2007
+Christoph Lameter, May 30, 2007