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304849a27b
htab_map_mem_usage() is introduced to calculate hashmap memory usage. In
this helper, some small memory allocations are ignore, as their size is
quite small compared with the total size. The inner_map_meta in
hash_of_map is also ignored.
The result for hashtab as follows,
- before this change
1: hash name count_map flags 0x1 <<<< no prealloc, fully set
key 16B value 24B max_entries 1048576 memlock 41943040B
2: hash name count_map flags 0x1 <<<< no prealloc, none set
key 16B value 24B max_entries 1048576 memlock 41943040B
3: hash name count_map flags 0x0 <<<< prealloc
key 16B value 24B max_entries 1048576 memlock 41943040B
The memlock is always a fixed size whatever it is preallocated or
not, and whatever the count of allocated elements is.
- after this change
1: hash name count_map flags 0x1 <<<< non prealloc, fully set
key 16B value 24B max_entries 1048576 memlock 117441536B
2: hash name count_map flags 0x1 <<<< non prealloc, non set
key 16B value 24B max_entries 1048576 memlock 16778240B
3: hash name count_map flags 0x0 <<<< prealloc
key 16B value 24B max_entries 1048576 memlock 109056000B
The memlock now is hashtab actually allocated.
The result for percpu hash map as follows,
- before this change
4: percpu_hash name count_map flags 0x0 <<<< prealloc
key 16B value 24B max_entries 1048576 memlock 822083584B
5: percpu_hash name count_map flags 0x1 <<<< no prealloc
key 16B value 24B max_entries 1048576 memlock 822083584B
- after this change
4: percpu_hash name count_map flags 0x0
key 16B value 24B max_entries 1048576 memlock 897582080B
5: percpu_hash name count_map flags 0x1
key 16B value 24B max_entries 1048576 memlock 922748736B
At worst, the difference can be 10x, for example,
- before this change
6: hash name count_map flags 0x0
key 4B value 4B max_entries 1048576 memlock 8388608B
- after this change
6: hash name count_map flags 0x0
key 4B value 4B max_entries 1048576 memlock 83889408B
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20230305124615.12358-4-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.