From: Waiman Long <llong@redhat.com>
To: Roman Gushchin <guro@fb.com>, Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Shakeel Butt <shakeelb@google.com>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v3 2/2] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches
Date: Wed, 5 May 2021 19:06:24 -0400 [thread overview]
Message-ID: <95ab4bdf-f373-f71d-cdf5-05ad6edbb772@redhat.com> (raw)
In-Reply-To: <YJMZ+542NVnbWgat@carbon.dhcp.thefacebook.com>
On 5/5/21 6:19 PM, Roman Gushchin wrote:
> On Wed, May 05, 2021 at 11:29:54PM +0200, Vlastimil Babka wrote:
>> On 5/5/21 8:32 PM, Roman Gushchin wrote:
>>> On Wed, May 05, 2021 at 08:02:06PM +0200, Vlastimil Babka wrote:
>>>> On 5/5/21 7:30 PM, Roman Gushchin wrote:
>>>>> On Wed, May 05, 2021 at 11:46:13AM -0400, Waiman Long wrote:
>>>>>> With this change, all the objcg pointer array objects will come from
>>>>>> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
>>>>>> both the recursive kfree() problem and non-freeable slab problem are
>>>>>> gone. Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer
>>>>>> have mixed accounted and unaccounted objects, this will slightly reduce
>>>>>> the number of objcg pointer arrays that need to be allocated and save
>>>>>> a bit of memory.
>>>>> Unfortunately the positive effect of this change will be likely
>>>>> reversed by a lower utilization due to a larger number of caches.
>>>>>
>>>>> Btw, I wonder if we also need a change in the slab caches merging procedure?
>>>>> KMALLOC_NORMAL caches should not be merged with caches which can potentially
>>>>> include accounted objects.
>>>> Good point. But looks like kmalloc* caches are extempt from all merging in
>>>> create_boot_cache() via
>>>>
>>>> s->refcount = -1; /* Exempt from merging for now */
>>> Wait, s->refcount is adjusted to 1 in create_kmalloc_cache() after calling
>>> into create_boot_cache?
>> Hmm I missed that
>>
>> Now I wonder why all kmalloc caches on my system have 0 aliases :)
>> cat /sys/kernel/slab/kmalloc-*/aliases
> Yeah, I noticed it too, it's a good question. And I remember a case from
> the past when it wasn't true (kmalloc-32 was shared with something else).
>
The criteria for cache merging require close to exact match in all
attributes with a size difference of no more than sizeof(void *). So it
is not easy to find a close match.
Cheers,
Longman
next prev parent reply other threads:[~2021-05-05 23:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 15:46 [PATCH v3 0/2] mm: memcg/slab: Fix objcg pointer array handling problem Waiman Long
2021-05-05 15:46 ` [PATCH v3 1/2] mm: memcg/slab: Properly set up gfp flags for objcg pointer array Waiman Long
2021-05-05 16:09 ` Shakeel Butt
2021-05-05 16:46 ` Roman Gushchin
2021-05-05 15:46 ` [PATCH v3 2/2] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Waiman Long
2021-05-05 16:06 ` Vlastimil Babka
2021-05-05 16:31 ` Waiman Long
2021-05-05 16:17 ` Shakeel Butt
2021-05-05 16:31 ` Waiman Long
2021-05-05 17:30 ` Roman Gushchin
2021-05-05 18:02 ` Vlastimil Babka
2021-05-05 18:18 ` Roman Gushchin
2021-05-05 18:31 ` Waiman Long
2021-05-05 18:38 ` Roman Gushchin
2021-05-05 18:56 ` Waiman Long
2021-05-05 18:32 ` Roman Gushchin
2021-05-05 21:29 ` Vlastimil Babka
2021-05-05 22:19 ` Roman Gushchin
2021-05-05 23:06 ` Waiman Long [this message]
2021-05-05 18:11 ` Waiman Long
2021-05-05 18:22 ` Roman Gushchin
2021-05-05 18:54 ` Waiman Long
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