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

[Szabolcs Nagy <Szabolcs.Nagy@arm.com>]

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.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>



> diff --git a/sysdeps/aarch64/hp-timing.h b/sysdeps/aarch64/hp-timing.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..f9822e725c227b3b57d508dc7d44cd7d2d04faf4
> --- /dev/null
> +++ b/sysdeps/aarch64/hp-timing.h
> @@ -0,0 +1,47 @@
> +/* High precision, low overhead timing functions.  AArch64 version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifndef _HP_TIMING_H
> +#define _HP_TIMING_H   1
> +
> +#include <time.h>
> +#include <stdint.h>
> +#include <hp-timing-common.h>
> +#include <libc-symbols.h>
> +
> +/* Don't use inline timer in ld.so.  */
> +#if IS_IN(rtld)
> +# define HP_TIMING_INLINE      (0)
> +#else
> +# define HP_TIMING_INLINE      (1)
> +#endif
> +
> +typedef uint64_t hp_timing_t;
> +
> +#define HP_TIMING_NOW(var) \
> +  __asm__ __volatile__ ("isb; mrs %0, cntvct_el0" : "=r" (var))
> +
> +/* Compute elapsed time in nanoseconds.  */
> +#undef HP_TIMING_DIFF
> +#define HP_TIMING_DIFF(Diff, Start, End)                       \
> +({  hp_timing_t freq;                                          \
> +    __asm__ __volatile__ ("mrs %0, cntfrq_el0" : "=r" (freq)); \
> +   (Diff) = ((End) - (Start)) * (UINT64_C(1000000000) / freq); \
> +})
> +
> +#endif /* hp-timing.h */