From: Vlastimil Babka <vbabka@suse.cz>
To: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Vasily Averin <vvs@virtuozzo.com>,
Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Pekka Enberg <penberg@kernel.org>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
Linux MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
kernel@openvz.org
Subject: Re: slabinfo shows incorrect active_objs ???
Date: Wed, 23 Feb 2022 01:32:36 +0100 [thread overview]
Message-ID: <fbe5ee4f-1bdb-052f-1d99-6b65eaef95e0@suse.cz> (raw)
In-Reply-To: <FCEEAED3-AEED-4B69-9466-94011E29B945@linux.dev>
On 2/23/22 01:07, Roman Gushchin wrote:
>
>> On Feb 22, 2022, at 3:08 PM, Vlastimil Babka <vbabka@suse.cz> wrote:
>>
>> On 2/22/22 21:59, Roman Gushchin wrote:
>>>
>>>> On Feb 22, 2022, at 4:10 AM, Vasily Averin <vvs@virtuozzo.com> wrote:
>>
>> BTW please To/Cc directly all slab maintainers on future slab related
>> threads (added now).
>>
>>>> On 22.02.2022 13:23, Hyeonggon Yoo wrote:
>>>>>>> On Tue, Feb 22, 2022 at 12:22:02PM +0300, Vasily Averin wrote:
>>>>>>> Dear all,
>>>>>>>
>>>>>>> I've found that /proc/slabinfo shows inadequate numbers of in-use slab objects.
>>>>>>> it assumes that all objects stored in cpu caches are always 100% in use.
>>>>
>>>>>> Is it a bug or perhaps a well-known feature that I missed?
>>>>> This is not a bug..
>>>>
>>>> Thank you for explanation,
>>>> I think it would be useful to document this somewhere. (Documnetation? man slabinfo ?)
>>>> Also I would like to know is it some (fast) way to get real numbers in userspace ?
>>>> crash is too fat for this task.
>>>> Do you know perhaps some other userspace utility or may be systemtap/drgn script?
>>>
>>> Btw, implementing fast slab counters independent from the sl*b implementation and the physical layout of data might be an interesting idea.
>>
>> Interesting idea, but merging will be an issue if we ever manage to
>> officially allow kfree() on object allocated by kmem_cache_alloc() - which
>> is now blocked by SLOB (there was a recent thread that stalled).
>
> Well, we can store an id somewhere (like right behind the object).
> Depending on the object size and padding it might even take not so much
> extra space. Maybe not the feature everybody needs (so it can be turned
> off by default), but something that can be really useful in some cases.
Hm it would be easier just to disable merging when the precise counters are
enabled. Assume it would be a config option (possibly boot-time option with
static keys) anyway so those who don't need them can avoid the overhead.
next prev parent reply other threads:[~2022-02-23 0:32 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-22 9:22 Vasily Averin
2022-02-22 10:23 ` Hyeonggon Yoo
2022-02-22 12:10 ` Vasily Averin
2022-02-22 16:32 ` Shakeel Butt
2022-02-22 16:47 ` Roman Gushchin
2022-02-23 1:07 ` Vasily Averin
2022-02-22 20:59 ` Roman Gushchin
2022-02-22 23:08 ` Vlastimil Babka
2022-02-23 0:07 ` Roman Gushchin
2022-02-23 0:32 ` Vlastimil Babka [this message]
2022-02-23 3:45 ` Hyeonggon Yoo
2022-02-23 17:31 ` Vlastimil Babka
2022-02-23 18:15 ` Roman Gushchin
2022-02-24 13:16 ` Vasily Averin
2022-02-25 0:08 ` Roman Gushchin
2022-02-25 4:37 ` Vasily Averin
2022-02-28 6:17 ` Vasily Averin
2022-02-28 10:22 ` Hyeonggon Yoo
2022-02-28 10:28 ` Hyeonggon Yoo
2022-02-28 10:43 ` Hyeonggon Yoo
2022-02-28 12:09 ` Hyeonggon Yoo
2022-03-03 8:39 ` Christoph Lameter
2022-03-04 16:29 ` Vlastimil Babka
2022-02-22 11:10 ` Vlastimil Babka
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