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Date: Fri, 10 Sep 2010 12:54:28 +0300
From: Phil Carmody <ext-phil.2.carmody@...ia.com>
To: mingo@...e.hu, gregkh@...e.de
Cc: linux-kernel@...r.kernel.org, travis@....com, akataria@...are.com
Subject: [PATCH 3/3] DO NOT INTEGRATE: test-only timing
Always run both the old and the converging method to see
what they would say, even if we have more accurate values.
Signed-off-by: Phil Carmody <ext-phil.2.carmody@...ia.com>
---
init/calibrate.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++---
1 files changed, 70 insertions(+), 4 deletions(-)
diff --git a/init/calibrate.c b/init/calibrate.c
index 7315c9a..b6d592e 100644
--- a/init/calibrate.c
+++ b/init/calibrate.c
@@ -146,6 +146,8 @@ static unsigned long __cpuinit calibrate_delay_converge(void)
* the largest likely undershoot. This defines our chop bounds.
*/
trials -= band;
+ pr_info("lpj underestimate = %lu * %i = %lu, band = %i\n",
+ lpj, trials, trials * lpj, band);
loopadd = lpj * band;
lpj *= trials;
chop_limit = lpj >> (LPS_PREC + 1);
@@ -169,32 +171,96 @@ static unsigned long __cpuinit calibrate_delay_converge(void)
return lpj;
}
+/* Old version for timing purposes only */
+static unsigned long __cpuinit calibrate_delay_converge_slowly(void)
+{
+ unsigned long lpj, ticks, loopbit;
+ int lps_precision = LPS_PREC;
+
+ lpj = (1<<12);
+ while ((lpj <<= 1) != 0) {
+ /* wait for "start of" clock tick */
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ /* Go .. */
+ ticks = jiffies;
+ __delay(lpj);
+ ticks = jiffies - ticks;
+ if (ticks)
+ break;
+ }
+
+ /*
+ * Do a binary approximation to get lpj set to
+ * equal one clock (up to lps_precision bits)
+ */
+ lpj >>= 1;
+ loopbit = lpj;
+ while (lps_precision-- && (loopbit >>= 1)) {
+ lpj |= loopbit;
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ ticks = jiffies;
+ __delay(lpj);
+ if (jiffies != ticks) /* longer than 1 tick */
+ lpj &= ~loopbit;
+ }
+
+ return lpj;
+}
+
+static void finally_print_bogomips(unsigned long lpj, unsigned int ticks)
+{
+ /* This calculation is bogus */
+ pr_cont("%lu.%02lu BogoMIPS (lpj=%lu) took %u jiffies\n",
+ lpj/(500000/HZ), (lpj/(5000/HZ)) % 100, lpj, ticks);
+}
+
void __cpuinit calibrate_delay(void)
{
+ enum methods { DUNNO, PRESET, FINE, DIRECT, CONVERGE };
static bool printed;
+ int method_used = DUNNO;
+ unsigned long ojiffs = jiffies;
if (preset_lpj) {
+ method_used = PRESET;
loops_per_jiffy = preset_lpj;
if (!printed)
pr_info("Calibrating delay loop (skipped) "
"preset value.. ");
} else if ((!printed) && lpj_fine) {
+ method_used = FINE;
loops_per_jiffy = lpj_fine;
pr_info("Calibrating delay loop (skipped), "
"value calculated using timer frequency.. ");
} else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) {
+ method_used = DIRECT;
if (!printed)
pr_info("Calibrating delay using timer "
"specific routine.. ");
} else {
+ method_used = CONVERGE;
if (!printed)
pr_info("Calibrating delay loop... ");
loops_per_jiffy = calibrate_delay_converge();
}
- if (!printed)
- pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
- loops_per_jiffy/(500000/HZ),
- (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
+ if (!printed) {
+ unsigned long tmp_lpj;
+ finally_print_bogomips(loops_per_jiffy, jiffies-ojiffs);
+ if (method_used != CONVERGE) {
+ ojiffs = jiffies;
+ pr_info("New-style converging method... ");
+ tmp_lpj = calibrate_delay_converge();
+ finally_print_bogomips(tmp_lpj, jiffies-ojiffs);
+ }
+ ojiffs = jiffies;
+ pr_info("Old-style converging method... ");
+ tmp_lpj = calibrate_delay_converge_slowly();
+ finally_print_bogomips(tmp_lpj, jiffies-ojiffs);
+ }
printed = true;
}
--
1.7.2.rc1.37.gf8c40
--
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