Re: [PATCH] RCU for low latency (experimental)

[Andrew Morton <akpm@osdl.org>]

Dipankar Sarma <dipankar@in.ibm.com> wrote:
>
> Here is the RCU patch for low scheduling latency Andrew was talking
> about in the other thread. I had done some measurements with
> amlat on a 2.4 GHz P4 xeon box with 256MB memory running dbench
> and it reduced worst case scheduling latencies from 800 microseconds
> to about 400 microseconds.
> 
> It uses per-cpu kernel threads to execute excess callbacks and
> pretty much relies on preemption.

Is simple enough.  Do you expect this will help with the route cache
reaping problem?  I do think it's a bit hard to justify purely on the basis
of the scheduling latency goodness.

> +			list_splice(&RCU_rcudlist(cpu), &list);
> +			INIT_LIST_HEAD(&RCU_rcudlist(cpu));

We have list_splice_init().