Re: [PATCH 3/7] benchtests: Add arc4random benchtest

[Noah Goldstein <goldstein.w.n@gmail.com>]

On Thu, Apr 14, 2022 at 2:48 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 14/04/2022 16:17, Noah Goldstein wrote:
> > On Wed, Apr 13, 2022 at 3:26 PM Adhemerval Zanella via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> >>
> >> It shows both throughput (total bytes obtained in the test duration)
> >> and latecy for both arc4random and arc4random_buf with different
> >> sizes.
> >>
> >> +
> >> +static void *
> >> +thr_arc4random_latency (void *closure)
> >> +{
> >> +  struct thr_arc4random_arg *arg = closure;
> >> +  arg->ret = arg->val == 0 ? bench_arc4random_latency ()
> >> +                          : bench_arc4random_buf_latency (arg->val);
> >> +  return NULL;
> >> +}
> >
> > I think the expectation is that the chacha calls will be cold,
> > maybe it is worth adding a cache flush of sorts between
> > calls. It may be some prefetching in the start will help the code in
> > that case but would only be a regression with the hot in L1
> > benchmarks.
> >
> > Can wait though this V1 looks fine.
>
> In fact I think just checking the call within a thread does not add
> much, specially since we don't have any single-thread lock optimization
> for internal locks.  I will remove it on v2 and maybe revise it in the
> future.

What do you mean single-thread lock optimization?