2006-03-31 05:56:00

by Ravikiran G Thirumalai

Subject: [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 <[email protected]>
Signed-off-by: Ravikiran Thirumalai <[email protected]>
Signed-off-by: Shai Fultheim <[email protected]>

Index: linux-2.6.16mm2/mm/slab.c
===================================================================
--- linux-2.6.16mm2.orig/mm/slab.c 2006-03-30 11:38:33.000000000 -0800
+++ linux-2.6.16mm2/mm/slab.c 2006-03-30 15:47:55.000000000 -0800
@@ -424,6 +424,7 @@ 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;
@@ -469,6 +470,7 @@ 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) \
@@ -488,6 +490,7 @@ 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)
@@ -3099,9 +3102,11 @@ static inline void __cache_free(struct k
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 {
@@ -3779,7 +3784,7 @@ static void print_slabinfo_header(struct
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_puts(m, " : shrinker stat <nr requested> <nr freed>");
@@ -3894,11 +3899,12 @@ static int s_show(struct seq_file *m, vo
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 */
{

2006-03-31 06:02:09

by Andrew Morton

Subject: Re: [patch] slab: add statistics for alien cache overflows

Ravikiran G Thirumalai <[email protected]> wrote:
>
> 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.

Does it break slabtop, and whatever else reads /proc/slabinfo?

2006-03-31 06:52:03

by Ravikiran G Thirumalai

Subject: Re: [patch] slab: add statistics for alien cache overflows

On Thu, Mar 30, 2006 at 10:01:35PM -0800, Andrew Morton wrote:
> Ravikiran G Thirumalai <[email protected]> wrote:
> >
> > 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.
>
> Does it break slabtop, and whatever else reads /proc/slabinfo?

These stats get compiled in only with DEBUG_SLAB. Even with DEBUG_SLAB
compiled in, slabtop does not break. I guess slabtop is not wired to read
these extra stats. Is there anything else that reads slabinfo apart from
slabtop? I could find only slabtop to be relevant with the procps package.

Thanks,
Kiran