161 lines
6.2 KiB
C
161 lines
6.2 KiB
C
/* High precision, low overhead timing functions. i686 version.
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Copyright (C) 1998 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef _HP_TIMING_H
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#define _HP_TIMING_H 1
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#include <string.h>
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#include <sys/param.h>
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#include <stdio-common/_itoa.h>
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/* The macros defined here use the timestamp counter in i586 and up versions
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of the x86 processors. They provide a very accurate way to measure the
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time with very little overhead. The time values themself have no real
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meaning, only differences are interesting.
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This version is for the i686 processors. The difference to the i586
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version is that the timerstamp register is unconditionally used. This is
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not the case for the i586 version where we have to perform runtime test
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whether the processor really has this capability. We have to make this
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distinction since the sysdeps/i386/i586 code is supposed to work on all
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platforms while the i686 already contains i686-specific code.
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The list of macros we need includes the following:
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- HP_TIMING_AVAIL: test for availability.
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- HP_TIMING_INLINE: this macro is non-zero if the functionality is not
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implemented using function calls but instead uses some inlined code
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which might simply consist of a few assembler instructions. We have to
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know this since we might want to use the macros here in places where we
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cannot make function calls.
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- hp_timing_t: This is the type for variables used to store the time
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values.
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- HP_TIMING_ZERO: clear `hp_timing_t' object.
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- HP_TIMING_NOW: place timestamp for current time in variable given as
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parameter.
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- HP_TIMING_DIFF_INIT: do whatever is necessary to be able to use the
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HP_TIMING_DIFF macro.
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- HP_TIMING_DIFF: compute difference between two times and store it
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in a third. Source and destination might overlap.
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- HP_TIMING_ACCUM: add time difference to another variable. This might
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be a bit more complicated to implement for some platforms as the
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operation should be thread-safe and 64bit arithmetic on 32bit platforms
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is not.
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- HP_TIMING_ACCUM_NT: this is the variant for situations where we know
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there are no threads involved.
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- HP_TIMING_PRINT: write decimal representation of the timing value into
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the given string. This operation need not be inline even though
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HP_TIMING_INLINE is specified.
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*/
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/* We always assume having the timestamp register. */
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#define HP_TIMING_AVAIL (1)
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/* We indeed have inlined functions. */
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#define HP_TIMING_INLINE (1)
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/* We use 64bit values for the times. */
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typedef unsigned long long int hp_timing_t;
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/* Internal variable used to store the overhead of the measurement
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opcodes. */
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extern hp_timing_t __libc_hp_timing_overhead;
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/* Set timestamp value to zero. */
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#define HP_TIMING_ZERO(Var) (Var) = (0)
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/* That's quite simple. Use the `rdtsc' instruction. Note that the value
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might not be 100% accurate since there might be some more instructions
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running in this moment. This could be changed by using a barrier like
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'cpuid' right before the `rdtsc' instruciton. But we are not interested
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in accurate clock cycles here so we don't do this. */
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#define HP_TIMING_NOW(Var) __asm__ __volatile__ ("rdtsc" : "=A" (Var))
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/* Use two 'rdtsc' instructions in a row to find out how long it takes. */
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#define HP_TIMING_DIFF_INIT() \
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do { \
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int __cnt = 5; \
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__libc_hp_timing_overhead = ~0ull; \
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do \
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{ \
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hp_timing_t __t1, __t2; \
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HP_TIMING_NOW (__t1); \
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HP_TIMING_NOW (__t2); \
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if (__t2 - __t1 < __libc_hp_timing_overhead) \
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__libc_hp_timing_overhead = __t2 - __t1; \
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} \
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while (--__cnt > 0); \
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} while (0)
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/* It's simple arithmetic for us. */
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#define HP_TIMING_DIFF(Diff, Start, End) (Diff) = ((End) - (Start))
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/* We have to jump through hoops to get this correctly implemented. */
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#define HP_TIMING_ACCUM(Sum, Diff) \
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do { \
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char __not_done; \
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hp_timing_t __oldval = (Sum); \
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hp_timing_t __diff = (Diff) - __libc_hp_timing_overhead; \
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do \
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{ \
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hp_timing_t __newval = __oldval + __diff; \
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int __temp0, __temp1; \
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__asm__ __volatile__ ("xchgl %4, %%ebx\n\t" \
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"lock; cmpxchg8b %1\n\t" \
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"sete %0\n\t" \
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"movl %4, %%ebx" \
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: "=q" (__not_done), "=m" (Sum), \
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"=A" (__oldval), "=c" (__temp0), \
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"=SD" (__temp1) \
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: "1" (Sum), "2" (__oldval), \
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"3" (__newval >> 32), \
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"4" (__newval & 0xffffffff) \
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: "memory"); \
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} \
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while (__not_done); \
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} while (0)
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/* No threads, no extra work. */
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#define HP_TIMING_ACCUM_NT(Sum, Diff) (Sum) += (Diff)
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/* Print the time value. */
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#define HP_TIMING_PRINT(Buf, Len, Val) \
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do { \
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char __buf[20]; \
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char *__cp = _itoa (Val, __buf + sizeof (__buf), 10, 0); \
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int __len = (Len); \
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char *__dest = (Buf); \
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while (__len-- > 0 && __cp < __buf + sizeof (__buf)) \
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*__dest++ = *__cp++; \
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memcpy (__dest, " clock cycles", MIN (__len, sizeof (" clock cycles"))); \
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} while (0)
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#endif /* hp-timing.h */
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