[Intel-gfx] [PATCH v3 1/6] cgroup: Allow registration and lookup of cgroup private data
tj at kernel.org
Tue Mar 13 20:50:35 UTC 2018
cc'ing Roman and Alexei.
On Tue, Mar 06, 2018 at 03:46:55PM -0800, Matt Roper wrote:
> There are cases where other parts of the kernel may wish to store data
> associated with individual cgroups without building a full cgroup
> controller. Let's add interfaces to allow them to register and lookup
> this private data for individual cgroups.
> A kernel system (e.g., a driver) that wishes to register private data
> for a cgroup will do so by subclassing the 'struct cgroup_priv'
> structure to describe the necessary data to store. Before registering a
> private data structure to a cgroup, the caller should fill in the 'key'
> and 'free' fields of the base cgroup_priv structure.
> * 'key' should be a unique void* that will act as a key for future
> privdata lookups/removals. Note that this allows drivers to store
> per-device private data for a cgroup by using a device pointer as a key.
> * 'free' should be a function pointer to a function that may be used
> to destroy the private data. This function will be called
> automatically if the underlying cgroup is destroyed.
This feature turned out to have more users than I originally
anticipated and bpf also wants something like this to track network
states. The requirements are pretty similar but not quite the same.
The extra requirements are...
* Lookup must be really cheap. Probably using pointer hash or walking
list isn't great, so maybe idr based lookup + RCU protected index
table per cgroup?
* It should support both regular memory and percpu pointers. Given
that what cgroup does is pretty much cgroup:key -> pointer lookup,
it's mostly about getting the interface right so that it's not too
Sorry about moving the goalpost.
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