On Mon, Feb 6, 2023 at 6:14 AM Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
>
> On Thu, Feb 02, 2023 at 01:41:58AM +0000, 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
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > ---
> > kernel/bpf/hashtab.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>
> What about other maps like regular array map?
>
I haven't finished the work to support all bpf maps.
Most of the maps have fixed entries, so we can get the usage directly
from an map pointer or get the element size and then calculate it, for
example,
- arraymap usage
size = kvsize(array);
- percpu arraymap usage
size = kvsize(array);
size += percpu_size(array->pptrs[0]) * array->map.max_entries;
But there's special case like cgroup_storage, the max_entries of which
is 0, for example,
122: cgroup_storage flags 0x0
key 16B value 8B max_entries 0 memlock 0B
For this case, we should calculate the count of entries first.
--
Regards
Yafang
