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authorJakub Jelinek <jakub@redhat.com>2007-07-12 18:26:36 +0000
committerJakub Jelinek <jakub@redhat.com>2007-07-12 18:26:36 +0000
commit0ecb606cb6cf65de1d9fc8a919bceb4be476c602 (patch)
tree2ea1f8305970753e4a657acb2ccc15ca3eec8e2c /sysdeps/powerpc/powerpc64/hp-timing.h
parent7d58530341304d403a6626d7f7a1913165fe2f32 (diff)
downloadglibc-0ecb606cb6cf65de1d9fc8a919bceb4be476c602.tar.gz
2.5-18.1
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+/* High precision, low overhead timing functions. powerpc64 version.
+ Copyright (C) 2005 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+ 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#ifndef _HP_TIMING_H
+#define _HP_TIMING_H 1
+
+#include <string.h>
+#include <sys/param.h>
+#include <stdio-common/_itoa.h>
+#include <atomic.h>
+
+/* The macros defined here use the powerpc 64-bit time base register.
+ The time base is nominally clocked at 1/8th the CPU clock, but this
+ can vary.
+
+ The list of macros we need includes the following:
+
+ - HP_TIMING_AVAIL: test for availability.
+
+ - HP_TIMING_INLINE: this macro is non-zero if the functionality is not
+ implemented using function calls but instead uses some inlined code
+ which might simply consist of a few assembler instructions. We have to
+ know this since we might want to use the macros here in places where we
+ cannot make function calls.
+
+ - hp_timing_t: This is the type for variables used to store the time
+ values.
+
+ - HP_TIMING_ZERO: clear `hp_timing_t' object.
+
+ - HP_TIMING_NOW: place timestamp for current time in variable given as
+ parameter.
+
+ - HP_TIMING_DIFF_INIT: do whatever is necessary to be able to use the
+ HP_TIMING_DIFF macro.
+
+ - HP_TIMING_DIFF: compute difference between two times and store it
+ in a third. Source and destination might overlap.
+
+ - HP_TIMING_ACCUM: add time difference to another variable. This might
+ be a bit more complicated to implement for some platforms as the
+ operation should be thread-safe and 64bit arithmetic on 32bit platforms
+ is not.
+
+ - HP_TIMING_ACCUM_NT: this is the variant for situations where we know
+ there are no threads involved.
+
+ - HP_TIMING_PRINT: write decimal representation of the timing value into
+ the given string. This operation need not be inline even though
+ HP_TIMING_INLINE is specified.
+
+*/
+
+/* We always assume having the timestamp register. */
+#define HP_TIMING_AVAIL (1)
+
+/* We indeed have inlined functions. */
+#define HP_TIMING_INLINE (1)
+
+/* We use 64bit values for the times. */
+typedef unsigned long long int hp_timing_t;
+
+/* Set timestamp value to zero. */
+#define HP_TIMING_ZERO(Var) (Var) = (0)
+
+/* That's quite simple. Use the `mftb' instruction. Note that the value
+ might not be 100% accurate since there might be some more instructions
+ running in this moment. This could be changed by using a barrier like
+ 'lwsync' right before the `mftb' instruciton. But we are not interested
+ in accurate clock cycles here so we don't do this. */
+#define HP_TIMING_NOW(Var) __asm__ __volatile__ ("mftb %0" : "=r" (Var))
+
+/* Use two 'mftb' instructions in a row to find out how long it takes.
+ On current POWER4, POWER5, and 970 processors mftb take ~10 cycles. */
+#define HP_TIMING_DIFF_INIT() \
+ do { \
+ if (GLRO(dl_hp_timing_overhead) == 0) \
+ { \
+ int __cnt = 5; \
+ GLRO(dl_hp_timing_overhead) = ~0ull; \
+ do \
+ { \
+ hp_timing_t __t1, __t2; \
+ HP_TIMING_NOW (__t1); \
+ HP_TIMING_NOW (__t2); \
+ if (__t2 - __t1 < GLRO(dl_hp_timing_overhead)) \
+ GLRO(dl_hp_timing_overhead) = __t2 - __t1; \
+ } \
+ while (--__cnt > 0); \
+ } \
+ } while (0)
+
+/* It's simple arithmetic in 64-bit. */
+#define HP_TIMING_DIFF(Diff, Start, End) (Diff) = ((End) - (Start))
+
+/* We need to insure that this add is atomic in threaded environments. We use
+ __arch_atomic_exchange_and_add_64 from atomic.h to get thread safety. */
+#define HP_TIMING_ACCUM(Sum, Diff) \
+ do { \
+ hp_timing_t __diff = (Diff) - GLRO(dl_hp_timing_overhead); \
+ __arch_atomic_exchange_and_add_64 (&(Sum), __diff); \
+ } while (0)
+
+/* No threads, no extra work. */
+#define HP_TIMING_ACCUM_NT(Sum, Diff) (Sum) += (Diff)
+
+/* Print the time value. */
+#define HP_TIMING_PRINT(Buf, Len, Val) \
+ do { \
+ char __buf[20]; \
+ char *__cp = _itoa (Val, __buf + sizeof (__buf), 10, 0); \
+ size_t __len = (Len); \
+ char *__dest = (Buf); \
+ while (__len-- > 0 && __cp < __buf + sizeof (__buf)) \
+ *__dest++ = *__cp++; \
+ memcpy (__dest, " ticks", MIN (__len, sizeof (" ticks"))); \
+ } while (0)
+
+#endif /* hp-timing.h */