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From: John Fastabend <john.fastabend@gmail.com>
To: Yafang Shao <laoar.shao@gmail.com>,
	ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
	john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org, tj@kernel.org,
	dennis@kernel.org, cl@linux.com, akpm@linux-foundation.org,
	penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
	roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, vbabka@suse.cz,
	urezki@gmail.com
Cc: linux-mm@kvack.org, bpf@vger.kernel.org,
	Yafang Shao <laoar.shao@gmail.com>
Subject: RE: [PATCH bpf-next 7/7] bpf: hashtab memory usage
Date: Fri, 03 Feb 2023 18:01:13 -0800	[thread overview]
Message-ID: <63ddbc69ef50f_6bb1520813@john.notmuch> (raw)
In-Reply-To: <20230202014158.19616-8-laoar.shao@gmail.com>

Yafang Shao wrote:
> Get htab memory usage from the htab pointers we have allocated. Some
> small pointers are ignored as their size are quite small compared with
> the total size.
> 
> The result as follows,
> - before this change
> 1: hash  name count_map  flags 0x0  <<<< prealloc
>         key 16B  value 24B  max_entries 1048576  memlock 41943040B
> 2: hash  name count_map  flags 0x1  <<<< non prealloc, fully set
>         key 16B  value 24B  max_entries 1048576  memlock 41943040B
> 3: hash  name count_map  flags 0x1  <<<< non prealloc, non set
>         key 16B  value 24B  max_entries 1048576  memlock 41943040B
> 
> The memlock is always a fixed number whatever it is preallocated or
> not, and whatever the allocated elements number is.
> 
> - after this change
> 1: hash  name count_map  flags 0x0  <<<< prealloc
>         key 16B  value 24B  max_entries 1048576  memlock 109064464B
> 2: hash  name count_map  flags 0x1  <<<< non prealloc, fully set
>         key 16B  value 24B  max_entries 1048576  memlock 117464320B
> 3: hash  name count_map  flags 0x1  <<<< non prealloc, non set
>         key 16B  value 24B  max_entries 1048576  memlock 16797952B
> 
> The memlock now is hashtab actually allocated.
> 
> At worst, the difference can be 10x, for example,
> - before this change
> 4: hash  name count_map  flags 0x0
>         key 4B  value 4B  max_entries 1048576  memlock 8388608B
> 
> - after this change
> 4: hash  name count_map  flags 0x0
>         key 4B  value 4B  max_entries 1048576  memlock 83898640B
> 

This walks the entire map and buckets to get the size? Inside a
rcu critical section as well :/ it seems.

What am I missing, if you know how many elements are added (which
you can track on map updates) how come we can't just calculate the
memory size directly from this?

Thanks,
John

  reply	other threads:[~2023-02-04  2:01 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-02  1:41 [PATCH bpf-next 0/7] bpf, mm: bpf memory usage Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 1/7] mm: percpu: fix incorrect size in pcpu_obj_full_size() Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 2/7] mm: percpu: introduce percpu_size() Yafang Shao
2023-02-02 14:32   ` Christoph Lameter
2023-02-02 15:01     ` Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 3/7] mm: vmalloc: introduce vsize() Yafang Shao
2023-02-02 10:23   ` Christoph Hellwig
2023-02-02 14:10     ` Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 4/7] mm: util: introduce kvsize() Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 5/7] bpf: add new map ops ->map_mem_usage Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 6/7] bpf: introduce bpf_mem_alloc_size() Yafang Shao
2023-02-02  4:53   ` kernel test robot
2023-02-02 14:11     ` Yafang Shao
2023-02-02  1:41 ` [PATCH bpf-next 7/7] bpf: hashtab memory usage Yafang Shao
2023-02-04  2:01   ` John Fastabend [this message]
2023-02-05  3:55     ` Yafang Shao
2023-02-08  1:56       ` Alexei Starovoitov
2023-02-08  3:33         ` Yafang Shao
2023-02-08  4:29           ` Alexei Starovoitov
2023-02-08 14:22             ` Yafang Shao
2023-02-05 22:14   ` Cong Wang
2023-02-06 11:52     ` Yafang Shao
2023-02-04  2:15 ` [PATCH bpf-next 0/7] bpf, mm: bpf " John Fastabend
2023-02-05  4:03   ` Yafang Shao
2023-02-07  0:48     ` Ho-Ren Chuang
2023-02-07  7:02       ` Yafang Shao
2023-02-07  0:53     ` Ho-Ren Chuang

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