Re: [PATCH] net/sock: move memory_allocated over to percpu_counter variables

[Eric Dumazet]

On Thu, Sep 6, 2018 at 12:21 PM Olof Johansson <olof@xxxxxxxxx> wrote:
>
> Today these are all global shared variables per protocol, and in
> particular tcp_memory_allocated can get hot on a system with
> large number of CPUs and a substantial number of connections.
>
> Moving it over to a per-cpu variable makes it significantly cheaper,
> and the added overhead when summing up the percpu copies is still smaller
> than the cost of having a hot cacheline bouncing around.

I am curious. We never noticed contention on this variable, at least for TCP.

Please share some numbers with us.