[PATCH v5 1/2] timer: lower rounding of TSC estimation to 100KHz

[Isaac Boukris]

In practice, the frequency is often not a nice round number, while
the estimation results are rather accurate, just a couple of KHz
away from the kernel's tsc_khz value, so it should suffice.

Rounding to 10MHz can cause a significant drift from real time,
up to a second per 10 minutes.

See also bugzilla: 959

Signed-off-by: Isaac Boukris <ibouk...@gmail.com>
---
 lib/eal/linux/eal_timer.c   | 6 +++---
 lib/eal/windows/eal_timer.c | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/eal/linux/eal_timer.c b/lib/eal/linux/eal_timer.c
index 1cb1e92193..f56a7ae15b 100644
--- a/lib/eal/linux/eal_timer.c
+++ b/lib/eal/linux/eal_timer.c
@@ -192,7 +192,7 @@ get_tsc_freq(void)
 {
 #ifdef CLOCK_MONOTONIC_RAW
 #define NS_PER_SEC 1E9
-#define CYC_PER_10MHZ 1E7
+#define CYC_PER_100KHZ 1E5
 
        struct timespec sleeptime = {.tv_nsec = NS_PER_SEC / 10 }; /* 1/10 
second */
 
@@ -209,8 +209,8 @@ get_tsc_freq(void)
 
                double secs = (double)ns/NS_PER_SEC;
                tsc_hz = (uint64_t)((end - start)/secs);
-               /* Round up to 10Mhz. 1E7 ~ 10Mhz */
-               return RTE_ALIGN_MUL_NEAR(tsc_hz, CYC_PER_10MHZ);
+               /* Round up to 100Khz. 1E5 ~ 100Khz */
+               return RTE_ALIGN_MUL_NEAR(tsc_hz, CYC_PER_100KHZ);
        }
 #endif
        return 0;
diff --git a/lib/eal/windows/eal_timer.c b/lib/eal/windows/eal_timer.c
index b070cb7751..4003541b08 100644
--- a/lib/eal/windows/eal_timer.c
+++ b/lib/eal/windows/eal_timer.c
@@ -12,7 +12,7 @@
 #include "eal_private.h"
 
 #define US_PER_SEC 1E6
-#define CYC_PER_10MHZ 1E7
+#define CYC_PER_100KHZ 1E5
 
 void
 rte_delay_us_sleep(unsigned int us)
@@ -81,8 +81,8 @@ get_tsc_freq(void)
        double secs = ((double)elapsed_us.QuadPart)/US_PER_SEC;
        tsc_hz = (uint64_t)((end - start)/secs);
 
-       /* Round up to 10Mhz. 1E7 ~ 10Mhz */
-       return RTE_ALIGN_MUL_NEAR(tsc_hz, CYC_PER_10MHZ);
+       /* Round up to 100Khz. 1E5 ~ 100Khz */
+       return RTE_ALIGN_MUL_NEAR(tsc_hz, CYC_PER_100KHZ);
 }
 
 
-- 
2.45.0