Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker_info on offlined nodes

[Michal Hocko]

On Mon 06-12-21 14:47:13, David Hildenbrand wrote:
> On 06.12.21 14:06, Michal Hocko wrote:
[...]
> > This is certainly possible. But it a) adds a branch to the hotpath and
> > b) it doesn't solve any other potential dereference of garbage node.
> 
> I don't think a) is  a problem but it's easy to measure.

Let me just clarify on this one. This single particular branch will be
indeed hard to match to any performance changes. On a single call of the
allocator it is nothing. But it is a condition that will be executed by
each caller while it won't ever trigger in most systems and workloads.

In other words it will cause a lot of wasted cpu cycles long term. A
more expensive one time initialization is worth in order to have
allocator fast path lighter IMHO.
-- 
Michal Hocko
SUSE Labs