Re: [PATCH v2] sched, timer: Use atomics for thread_group_cputimer to improve scalability

Linus Torvalds
2015-03-19T17:59:12Z

On Thu, Mar 19, 2015 at 10:21 AM, Jason Low <jason.low2@hp.com> wrote:
>
> I tested this patch on a 32 bit ARM system with 4 cores. Using the
> generic 64 bit atomics, I did not see any performance change with this
> patch, and the relevant functions (account_group_*_time(), ect...) don't
> show up in perf reports.

Ok.

> One factor might be because locking/cacheline contention isn't as
> apparent on smaller systems to begin with, and lib/atomic64.c also
> mentions that "this is expected to used on systems with small numbers of
> CPUs (<= 4 or so)".

Yeah, that's probably a valid argument anyway - 32-bit systems aren't
really going to be multi-node big systems any more.

So I'm ok with the patch,

Linus