[dpdk-dev] [PATCH v6] eal: add tsc_hz to rte_mem_config

[Jim Harris <james.r.harris@intel.com>]

This ensures secondary processes never have to
calculate the TSC rate themselves, which can be
noticeable in VMs that don't have access to
arch-specific detection mechanism (such as
CPUID leaf 0x15 or MSR 0xCE on x86).

Since rte_mem_config is now internal to the rte_eal
library, we can add tsc_hz without ABI breakage
concerns.

Reduces rte_eal_init() execution time in a secondary
process from 165ms to 66ms on my test system.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
---
 lib/librte_eal/common/eal_common_timer.c |   15 +++++++++++++++
 lib/librte_eal/common/eal_memcfg.h       |    3 +++
 2 files changed, 18 insertions(+)

diff --git a/lib/librte_eal/common/eal_common_timer.c b/lib/librte_eal/common/eal_common_timer.c
index 145543de7..fa9ee1b22 100644
--- a/lib/librte_eal/common/eal_common_timer.c
+++ b/lib/librte_eal/common/eal_common_timer.c
@@ -15,8 +15,10 @@
 #include <rte_log.h>
 #include <rte_cycles.h>
 #include <rte_pause.h>
+#include <rte_eal.h>
 
 #include "eal_private.h"
+#include "eal_memcfg.h"
 
 /* The frequency of the RDTSC timer resolution */
 static uint64_t eal_tsc_resolution_hz;
@@ -77,8 +79,20 @@ estimate_tsc_freq(void)
 void
 set_tsc_freq(void)
 {
+	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
 	uint64_t freq;
 
+	if (rte_eal_process_type() == RTE_PROC_SECONDARY) {
+		/*
+		 * Just use the primary process calculated TSC rate in any
+		 * secondary process.  It avoids any unnecessary overhead on
+		 * systems where arch-specific frequency detection is not
+		 * available.
+		 */
+		eal_tsc_resolution_hz = mcfg->tsc_hz;
+		return;
+	}
+
 	freq = get_tsc_freq_arch();
 	if (!freq)
 		freq = get_tsc_freq();
@@ -87,6 +101,7 @@ set_tsc_freq(void)
 
 	RTE_LOG(DEBUG, EAL, "TSC frequency is ~%" PRIu64 " KHz\n", freq / 1000);
 	eal_tsc_resolution_hz = freq;
+	mcfg->tsc_hz = freq;
 }
 
 void rte_delay_us_callback_register(void (*userfunc)(unsigned int))
diff --git a/lib/librte_eal/common/eal_memcfg.h b/lib/librte_eal/common/eal_memcfg.h
index 359beb216..73be6fbae 100644
--- a/lib/librte_eal/common/eal_memcfg.h
+++ b/lib/librte_eal/common/eal_memcfg.h
@@ -70,6 +70,9 @@ struct rte_mem_config {
 	uint32_t single_file_segments;
 	/**< stored single file segments parameter. */
 
+	uint64_t tsc_hz;
+	/**< TSC rate */
+
 	uint8_t dma_maskbits; /**< Keeps the more restricted dma mask. */
 };