| Re: [PATCH] Show slab memory usage on OOM and SysRq-M [message #12097 is a reply to message #12083] |
Tue, 17 April 2007 13:22  |
Pekka Enberg
Messages: 22
Registered: November 2006
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Junior Member |
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Hi,
On 4/17/07, Pavel Emelianov <xemul@sw.ru> wrote:
> The out_of_memory() function and SysRq-M handler call
> show_mem() to show the current memory usage state.
>
> This is also helpful to see which slabs are the largest
> in the system.
Makes sense.
On 4/17/07, Pavel Emelianov <xemul@sw.ru> wrote:
> diff --git a/mm/slab.c b/mm/slab.c
> index 21b3c61..9a5829a 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -749,6 +749,7 @@ static inline void init_lock_keys(void)
> * 2. Protect sanity of cpu_online_map against cpu hotplug events
> */
> static DEFINE_MUTEX(cache_chain_mutex);
> +static DEFINE_SPINLOCK(cache_chain_lock);
So, now we have two locks protecting cache_chain? Please explain why
you can't use the mutex.
> +static unsigned long get_cache_size(struct kmem_cache *cachep)
> +{
> + unsigned long slabs;
> + struct kmem_list3 *l3;
> + struct list_head *lh;
> + int node;
> +
> + slabs = 0;
> +
> + for_each_online_node (node) {
> + l3 = cachep->nodelists[node];
> + if (l3 == NULL)
> + continue;
> +
> + spin_lock(&l3->list_lock);
> + list_for_each (lh, &l3->slabs_full)
> + slabs++;
> + list_for_each (lh, &l3->slabs_partial)
> + slabs++;
> + list_for_each (lh, &l3->slabs_free)
> + slabs++;
> + spin_unlock(&l3->list_lock);
> + }
> +
> + return slabs * ((PAGE_SIZE << cachep->gfporder) +
> + (OFF_SLAB(cachep) ? cachep->slabp_cache->buffer_size : 0));
> +}
Considering you're doing this at out_of_memory() time, wouldn't it
make more sense to add a ->nr_pages to struct kmem_cache and do the
tracking in kmem_getpages/kmem_freepages?
I would also drop the OFF_SLAB bits because it really doesn't matter
that much for your purposes. Besides, you're already per-node and
per-CPU caches here which attribute to much more memory on NUMA setups
for example.
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