Re: [PATCH v2 0/3] Directed kmem charging

[Shakeel Butt <shakeelb@google.com>]

On Wed, Feb 21, 2018 at 8:09 AM, Christopher Lameter <cl@linux.com> wrote:
> Another way to solve this is to switch the user context right?
>
> Isnt it possible to avoid these patches if do the allocation in another
> task context instead?
>

Sorry, can you please explain what you mean by 'switch the user
context'. Is there any example in kernel which does something similar?

Another way is by adding a field 'remote_memcg_to_charge' in
task_struct and set it before the allocation and in memcontrol.c,
first check if current->remote_memcg_to_charge is set otherwise use
the memcg of current. Also if we provide a wrapper to do that for the
user, there will be a lot less plumbing.

Please let me know if you prefer this approach.


> Are there really any other use cases beyond fsnotify?
>

Another use case I have in mind and plan to upstream is to bind a
filesystem mount with a memcg. So, all the file pages (or anon pages
for shmem) and kmem (like inodes and dentry) will be charged to that
memcg.

>
> The charging of the memory works on a per page level but the allocation
> occur from the same page for multiple tasks that may be running on a
> system. So how relevant is this for other small objects?
>
> Seems that if you do a large amount of allocations for the same purpose
> your chance of accounting it to the right memcg increases. But this is a
> game of chance.
>
>
>

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