| Re: [PATCH] Show slab memory usage on OOM and SysRq-M [message #12091 is a reply to message #12083] |
Tue, 17 April 2007 15:12   |
Eric Dumazet
Messages: 36
Registered: July 2006
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Member |
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On Tue, 17 Apr 2007 16:22:48 +0300
"Pekka Enberg" <penberg@cs.helsinki.fi> wrote:
> Hi,
>
> On 4/17/07, Pavel Emelianov <xemul@sw.ru> wrote:
> > +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?
>
To avoid a deadlock ? yes...
This nr_pages should be in struct kmem_list3, not in struct kmem_cache, or else you defeat NUMA optimizations if touching a field in kmem_cache at kmem_getpages()/kmem_freepages() time.
for_each_online_node (node) {
l3 = cachep->nodelists[node];
if (l3)
slabs += l3->nr_pages; /* dont lock l3->list_lock */
}
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