Re: [PATCH] AArch64: Add hp-timing.h

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 6/30/21 2:25 PM, Florian Weimer via Libc-alpha wrote:
> * Szabolcs Nagy via Libc-alpha:
> 
>> The 06/28/2021 11:11, Wilco Dijkstra wrote:
>>> Add hp-timing.h using the cntcvt_el0 counter. Return timing in nanoseconds
>>> so it is fully compatible with generic hp-timing. Don't set HP_TIMING_INLINE
>>> in the dynamic linker since very old kernels may not handle cntcvt correctly.
>>
>> can you please add a comment here that this
>> is only used in internal benchmarks and not
>> in installed glibc binaries. with that it's
>> ok to commit.
> 
> This commit would not be entirely accurate.  We install and ship the
> benchtests, so they need to use a stable ISA (and kernel ABI).

That doesn't seem like a reasonable limitation for benchtests.

> If the benchtests are like the testsuite and are not intended to be
> installed and distributed, we probably need to make downstream changes.

There's value in having the benchtest binaries in the distribution too, 
so maybe we need to figure out a way to do both, i.e. not be bound by 
ABI restrictions and at the same time, be deployable to do performance 
comparison.

Siddhesh