On 04/22/2014 02:30 PM, Michal Hocko wrote:
> On Fri 18-04-14 13:08:17, Andrew Morton wrote:
> [...]
>> From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
>> Subject: slub: fix memcg_propagate_slab_attrs
>>
>> After creating a cache for a memcg we should initialize its sysfs attrs
>> with the values from its parent. That's what memcg_propagate_slab_attrs
>> is for. Currently it's broken - we clearly muddled root-vs-memcg caches
>> there. Let's fix it up.
>
> Andrew didn't so I'll do. What is the effect of the mismatch? I am
> really drowning in that code...
If we tune a kmem cache's params via sysfs and then create a memcg that
wants to allocate from the cache, the memcg's copy of the cache will
have default values of the sysfs params instead of those of the global
cache.
>
>> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
>> Cc: Christoph Lameter <cl@xxxxxxxxx>
>> Cc: Pekka Enberg <penberg@xxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxx>
>> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
>> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> ---
>>
>> mm/slub.c | 11 +++++++----
>> 1 file changed, 7 insertions(+), 4 deletions(-)
>>
>> diff -puN mm/slub.c~slub-fix-memcg_propagate_slab_attrs mm/slub.c
>> --- a/mm/slub.c~slub-fix-memcg_propagate_slab_attrs
>> +++ a/mm/slub.c
>> @@ -5071,15 +5071,18 @@ static void memcg_propagate_slab_attrs(s
>> #ifdef CONFIG_MEMCG_KMEM
>> int i;
>> char *buffer = NULL;
>> + struct kmem_cache *root_cache;
>>
>> - if (!is_root_cache(s))
>> + if (is_root_cache(s))
>> return;
>>
>> + root_cache = s->memcg_params->root_cache;
>> +
>> /*
>> * This mean this cache had no attribute written. Therefore, no point
>> * in copying default values around
>> */
>> - if (!s->max_attr_size)
>> + if (!root_cache->max_attr_size)
>> return;
>>
>> for (i = 0; i < ARRAY_SIZE(slab_attrs); i++) {
>> @@ -5101,7 +5104,7 @@ static void memcg_propagate_slab_attrs(s
>> */
>> if (buffer)
>> buf = buffer;
>> - else if (s->max_attr_size < ARRAY_SIZE(mbuf))
>> + else if (root_cache->max_attr_size < ARRAY_SIZE(mbuf))
>> buf = mbuf;
>> else {
>> buffer = (char *) get_zeroed_page(GFP_KERNEL);
>> @@ -5110,7 +5113,7 @@ static void memcg_propagate_slab_attrs(s
>> buf = buffer;
>> }
>>
>> - attr->show(s->memcg_params->root_cache, buf);
>> + attr->show(root_cache, buf);
>> attr->store(s, buf, strlen(buf));
>> }
>>
>> _
>>
>> Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
>>
>> slub-fix-memcg_propagate_slab_attrs.patch
>> slb-charge-slabs-to-kmemcg-explicitly.patch
>> mm-get-rid-of-__gfp_kmemcg.patch
>> mm-get-rid-of-__gfp_kmemcg-fix.patch
>> slab-document-kmalloc_order.patch
>>
>
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