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

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

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.