[PATCH] slab: add statistics for alien cache overflows

Add a statistics counter which is incremented everytime the alien cache
overflows.  alien_cache limit is hardcoded to 12 right now.  We can use
this statistics to tune alien cache if needed in the future.

Signed-off-by: Alok N Kataria <alokk@calsoftinc.com>
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/mm/slab.c b/mm/slab.c
index afabad54c4c..752c5570f2f 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -420,6 +420,7 @@ struct kmem_cache {
         unsigned long max_freeable;
         unsigned long node_allocs;
         unsigned long node_frees;
+        unsigned long node_overflow;
         atomic_t allochit;
         atomic_t allocmiss;
         atomic_t freehit;
@@ -465,6 +466,7 @@ struct kmem_cache {
 #define STATS_INC_ERR(x)        ((x)->errors++)
 #define STATS_INC_NODEALLOCS(x) ((x)->node_allocs++)
 #define STATS_INC_NODEFREES(x)  ((x)->node_frees++)
+#define STATS_INC_ACOVERFLOW(x)   ((x)->node_overflow++)
 #define STATS_SET_FREEABLE(x, i)                                        \
         do {                                                            \
                 if ((x)->max_freeable < i)                              \
@@ -484,6 +486,7 @@ struct kmem_cache {
 #define STATS_INC_ERR(x)        do { } while (0)
 #define STATS_INC_NODEALLOCS(x) do { } while (0)
 #define STATS_INC_NODEFREES(x)  do { } while (0)
+#define STATS_INC_ACOVERFLOW(x)   do { } while (0)
 #define STATS_SET_FREEABLE(x, i) do { } while (0)
 #define STATS_INC_ALLOCHIT(x)   do { } while (0)
 #define STATS_INC_ALLOCMISS(x)  do { } while (0)
@@ -3083,9 +3086,11 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp)
                         if (l3->alien && l3->alien[nodeid]) {
                                 alien = l3->alien[nodeid];
                                 spin_lock(&alien->lock);
-                                if (unlikely(alien->avail == alien->limit))
+                                if (unlikely(alien->avail == alien->limit)) {
+                                        STATS_INC_ACOVERFLOW(cachep);
                                         __drain_alien_cache(cachep,
                                                             alien, nodeid);
+                                }
                                 alien->entry[alien->avail++] = objp;
                                 spin_unlock(&alien->lock);
                         } else {
@@ -3763,7 +3768,7 @@ static void print_slabinfo_header(struct seq_file *m)
         seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
 #if STATS
         seq_puts(m, " : globalstat <listallocs> <maxobjs> <grown> <reaped> "
-                 "<error> <maxfreeable> <nodeallocs> <remotefrees>");
+                 "<error> <maxfreeable> <nodeallocs> <remotefrees> <alienoverflow>");
         seq_puts(m, " : cpustat <allochit> <allocmiss> <freehit> <freemiss>");
 #endif
         seq_putc(m, '\n');
@@ -3877,11 +3882,12 @@ static int s_show(struct seq_file *m, void *p)
                 unsigned long max_freeable = cachep->max_freeable;
                 unsigned long node_allocs = cachep->node_allocs;
                 unsigned long node_frees = cachep->node_frees;
+                unsigned long overflows = cachep->node_overflow;
 
                 seq_printf(m, " : globalstat %7lu %6lu %5lu %4lu \
-                                %4lu %4lu %4lu %4lu", allocs, high, grown,
+                                %4lu %4lu %4lu %4lu %4lu", allocs, high, grown,
                                 reaped, errors, max_freeable, node_allocs,
-                                node_frees);
+                                node_frees, overflows);
         }
         /* cpu stats */
         {