Re: [PATCH-next] mm, memcg: Add ":deact" tag for reparented kmem caches in memcg_slabinfo
From: Waiman Long
Date: Thu Jun 27 2019 - 14:45:11 EST
On 6/26/19 3:58 PM, Roman Gushchin wrote:
> On Fri, Jun 21, 2019 at 01:30:05PM -0400, Waiman Long wrote:
>> With Roman's kmem cache reparent patch, multiple kmem caches of the same
>> type can be seen attached to the same memcg id. All of them, except
>> maybe one, are reparent'ed kmem caches. It can be useful to tag those
>> reparented caches by adding a new slab flag "SLAB_DEACTIVATED" to those
>> kmem caches that will be reparent'ed if it cannot be destroyed completely.
>> For the reparent'ed memcg kmem caches, the tag ":deact" will now be
>> shown in <debugfs>/memcg_slabinfo.
>> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> Hi Waiman!
> Sorry for the late reply. The patch overall looks good to me,
> except one nit. Please feel free to use my ack:
> Acked-by: Roman Gushchin <guro@xxxxxx>
>> include/linux/slab.h | 4 ++++
>> mm/slab.c | 1 +
>> mm/slab_common.c | 14 ++++++++------
>> mm/slub.c | 1 +
>> 4 files changed, 14 insertions(+), 6 deletions(-)
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index fecf40b7be69..19ab1380f875 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -116,6 +116,10 @@
>> /* Objects are reclaimable */
>> #define SLAB_RECLAIM_ACCOUNT ((slab_flags_t __force)0x00020000U)
>> #define SLAB_TEMPORARY SLAB_RECLAIM_ACCOUNT /* Objects are short-lived */
>> +/* Slab deactivation flag */
>> +#define SLAB_DEACTIVATED ((slab_flags_t __force)0x10000000U)
>> * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
>> diff --git a/mm/slab.c b/mm/slab.c
>> index a2e93adf1df0..e8c7743fc283 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -2245,6 +2245,7 @@ int __kmem_cache_shrink(struct kmem_cache *cachep)
>> #ifdef CONFIG_MEMCG
>> void __kmemcg_cache_deactivate(struct kmem_cache *cachep)
>> + cachep->flags |= SLAB_DEACTIVATED;
> A nit: it can be done from kmemcg_cache_deactivate() instead,
> and then you don't have to do it in slab and slub separately.
> Since it's not slab- or slub-specific code, it'd be better, IMO,
> to put it into slab_common.c.
Thanks for the suggestion.
You are right. It will be cleaner to set the flag in
kmemcg_cache_deactivate(). I have just sent out a v2 patch to do that.