From: Arthur de Kerhor <arthurdekerhor@gmail.com>
Date: Tue, 17 Jun 2025 14:30:51 +0000 (+0200)
Subject: policer: don't compute CPU clock frequency for each API call
X-Git-Tag: v26.02-rc0~206
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F17%2F43217%2F10;p=vpp.git

policer: don't compute CPU clock frequency for each API call

In some virtualized environments, where we can't get TSC from
clib_get_cpuid, os_cpu_clock_frequency can take more than 1ms
to return. As the TSC value is invariant over time, it can be
cached in policer_init instead of being recalculated everytime
a policer is created/updated.

Type: improvement
Change-Id: Icfd00feac76f35d562546a17e4830efb91dba219
Signed-off-by: Arthur de Kerhor <arthurdekerhor@gmail.com>
---

diff --git a/src/vnet/policer/policer.c b/src/vnet/policer/policer.c
index 00180d9c993..a24edb3c127 100644
--- a/src/vnet/policer/policer.c
+++ b/src/vnet/policer/policer.c
@@ -1037,6 +1037,19 @@ VLIB_CLI_COMMAND (show_policer_pools_command, static) = {
     .function = show_policer_pools_command_fn,
 };
 
+/*
+ * Return the number of hardware TSC timer ticks per second for the dataplane.
+ * This is approximately, but not exactly, the clock speed.
+ */
+static u64
+get_tsc_hz (void)
+{
+  f64 cpu_freq;
+
+  cpu_freq = os_cpu_clock_frequency ();
+  return (u64) cpu_freq;
+}
+
 clib_error_t *
 policer_init (vlib_main_t * vm)
 {
@@ -1052,6 +1065,7 @@ policer_init (vlib_main_t * vm)
 
   pm->policer_config_by_name = hash_create_string (0, sizeof (uword));
   pm->policer_index_by_name = hash_create_string (0, sizeof (uword));
+  pm->tsc_hz = get_tsc_hz ();
 
   vnet_classify_register_unformat_policer_next_index_fn
     (unformat_policer_classify_next_index);
diff --git a/src/vnet/policer/policer.h b/src/vnet/policer/policer.h
index 7ce7fc79d47..9eef408fd86 100644
--- a/src/vnet/policer/policer.h
+++ b/src/vnet/policer/policer.h
@@ -50,6 +50,9 @@ typedef struct
   /* frame queue for thread handoff */
   u32 fq_index[VLIB_N_RX_TX];
 
+  /* cached TSC value. No need to re-compute for each new policer */
+  u64 tsc_hz;
+
   u16 msg_id_base;
 } vnet_policer_main_t;
 
diff --git a/src/vnet/policer/xlate.c b/src/vnet/policer/xlate.c
index bffd208716d..26b0f593b14 100644
--- a/src/vnet/policer/xlate.c
+++ b/src/vnet/policer/xlate.c
@@ -843,19 +843,6 @@ pol_compute_hw_params (qos_pol_cfg_params_st *cfg, qos_pol_hw_params_st *hw)
   return 0;
 }
 
-/*
- * Return the number of hardware TSC timer ticks per second for the dataplane.
- * This is approximately, but not exactly, the clock speed.
- */
-static u64
-get_tsc_hz (void)
-{
-  f64 cpu_freq;
-
-  cpu_freq = os_cpu_clock_frequency ();
-  return (u64) cpu_freq;
-}
-
 /*
  * Convert rates into bytes_per_period and scale.
  * Return 0 if ok or 1 if error.
@@ -948,8 +935,8 @@ compute_policer_params (u64 hz,	      /* CPU speed in clocks per second */
 int
 x86_pol_compute_hw_params (qos_pol_cfg_params_st *cfg, policer_t *hw)
 {
+  vnet_policer_main_t *pm = &vnet_policer_main;
   const int BYTES_PER_KBIT = (1000 / 8);
-  u64 hz;
   u32 cap;
 
   if (!cfg || !hw)
@@ -958,7 +945,6 @@ x86_pol_compute_hw_params (qos_pol_cfg_params_st *cfg, policer_t *hw)
       return (-1);
     }
 
-  hz = get_tsc_hz ();
   hw->last_update_time = 0;
 
   /*
@@ -1001,10 +987,9 @@ x86_pol_compute_hw_params (qos_pol_cfg_params_st *cfg, policer_t *hw)
 	  return (-1);
 	}
 
-      if (compute_policer_params (hz,
-				  (u64) cfg->rb.kbps.cir_kbps *
-				  BYTES_PER_KBIT, 0, &hw->current_limit,
-				  &hw->extended_limit,
+      if (compute_policer_params (pm->tsc_hz,
+				  (u64) cfg->rb.kbps.cir_kbps * BYTES_PER_KBIT,
+				  0, &hw->current_limit, &hw->extended_limit,
 				  &hw->cir_tokens_per_period,
 				  &hw->pir_tokens_per_period, &hw->scale))
 	{
@@ -1025,14 +1010,11 @@ x86_pol_compute_hw_params (qos_pol_cfg_params_st *cfg, policer_t *hw)
 	  return (-1);
 	}
 
-      if (compute_policer_params (hz,
-				  (u64) cfg->rb.kbps.cir_kbps *
-				  BYTES_PER_KBIT,
-				  (u64) cfg->rb.kbps.eir_kbps *
-				  BYTES_PER_KBIT, &hw->current_limit,
-				  &hw->extended_limit,
-				  &hw->cir_tokens_per_period,
-				  &hw->pir_tokens_per_period, &hw->scale))
+      if (compute_policer_params (
+	    pm->tsc_hz, (u64) cfg->rb.kbps.cir_kbps * BYTES_PER_KBIT,
+	    (u64) cfg->rb.kbps.eir_kbps * BYTES_PER_KBIT, &hw->current_limit,
+	    &hw->extended_limit, &hw->cir_tokens_per_period,
+	    &hw->pir_tokens_per_period, &hw->scale))
 	{
 	  QOS_DEBUG_ERROR ("Policer parameter computation failed.");
 	  return (-1);