diff options
| -rw-r--r-- | Documentation/vm/slub.txt | 10 | ||||
| -rw-r--r-- | mm/slub.c | 41 |
2 files changed, 48 insertions, 3 deletions
diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index bb1f5c6e28b..510917ff59e 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: diff --git a/mm/slub.c b/mm/slub.c index a9201d83178..466089cd5de 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -142,6 +142,13 @@ SLAB_POISON | SLAB_STORE_USER) /* + * Debugging flags that require metadata to be stored in the slab, up to + * DEBUG_SIZE in size. + */ +#define DEBUG_SIZE_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER) +#define DEBUG_SIZE (3 * sizeof(void *) + 2 * sizeof(struct track)) + +/* * Set of flags that will prevent slab merging */ #define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \ @@ -326,6 +333,7 @@ static int slub_debug; #endif static char *slub_debug_slabs; +static int disable_higher_order_debug; /* * Object debugging @@ -977,6 +985,15 @@ static int __init setup_slub_debug(char *str) */ goto check_slabs; + if (tolower(*str) == 'o') { + /* + * Avoid enabling debugging on caches if its minimum order + * would increase as a result. + */ + disable_higher_order_debug = 1; + goto out; + } + slub_debug = 0; if (*str == '-') /* @@ -1023,13 +1040,27 @@ static unsigned long kmem_cache_flags(unsigned long objsize, unsigned long flags, const char *name, void (*ctor)(void *)) { + int debug_flags = slub_debug; + /* * Enable debugging if selected on the kernel commandline. */ - if (slub_debug && (!slub_debug_slabs || - strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)) == 0)) - flags |= slub_debug; + if (debug_flags) { + if (slub_debug_slabs && + strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs))) + goto out; + + /* + * Disable debugging that increases slab size if the minimum + * slab order would have increased as a result. + */ + if (disable_higher_order_debug && + get_order(objsize + DEBUG_SIZE) > get_order(objsize)) + debug_flags &= ~DEBUG_SIZE_FLAGS; + flags |= debug_flags; + } +out: return flags; } #else @@ -1561,6 +1592,10 @@ slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid) "default order: %d, min order: %d\n", s->name, s->objsize, s->size, oo_order(s->oo), oo_order(s->min)); + if (oo_order(s->min) > get_order(s->objsize)) + printk(KERN_WARNING " %s debugging increased min order, use " + "slub_debug=O to disable.\n", s->name); + for_each_online_node(node) { struct kmem_cache_node *n = get_node(s, node); unsigned long nr_slabs; |