Re: [PATCH v3 07/11] mm: vmalloc: Offload free_vmap_area_lock lock

Uladzislau Rezki
2024-01-11T15:54:53Z

On Thu, Jan 11, 2024 at 08:02:16PM +1100, Dave Chinner wrote:
> On Tue, Jan 02, 2024 at 07:46:29PM +0100, Uladzislau Rezki (Sony) wrote:
> > Concurrent access to a global vmap space is a bottle-neck.
> > We can simulate a high contention by running a vmalloc test
> > suite.
> >
> > To address it, introduce an effective vmap node logic. Each
> > node behaves as independent entity. When a node is accessed
> > it serves a request directly(if possible) from its pool.
> >
> > This model has a size based pool for requests, i.e. pools are
> > serialized and populated based on object size and real demand.
> > A maximum object size that pool can handle is set to 256 pages.
> >
> > This technique reduces a pressure on the global vmap lock.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
>
> Why not use a llist for this? That gets rid of the need for a
> new pool_lock altogether...
>
Initially i used the llist. I have changed it because i keep track
of objects per a pool to decay it later. I do not find these locks
as contented one therefore i did not think much.

Anyway, i will have a look at this to see if llist is easy to go with
or not. If so i will send out a separate patch.

Thanks!

--
Uladzislau Rezki