From: Vlastimil Babka <vbabka@suse.cz>
To: Roman Gushchin <guro@fb.com>
Cc: Waiman Long <longman@redhat.com>,
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 23:29:54 +0200 [thread overview]
Message-ID: <f73cc1c6-2950-c56d-6a57-8cebb23db65b@suse.cz> (raw)
In-Reply-To: <YJLk1tmDeGed58yr@carbon.dhcp.thefacebook.com>
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
> It means they are not exempt actually.
>
next prev parent reply other threads:[~2021-05-05 21:29 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 [this message]
2021-05-05 22:19 ` Roman Gushchin
2021-05-05 23:06 ` Waiman Long
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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