interface: add pcap trace data preallocation

Type: improvement

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I2e53fa85a0b4082666f57a3a58a09c04ae2001b5

2 files changed, 48 insertions, 4 deletions

diff --git a/src/vnet/interface.h b/src/vnet/interface.h
index 5f4fd065756..f9081442338 100644
--- a/src/vnet/interface.h
+++ b/src/vnet/interface.h
@@ -924,6 +924,8 @@ typedef struct
   u8 rx_enable;
   u8 tx_enable;
   u8 drop_enable;
+  u8 preallocate_data;
+  u8 free_data;
   u32 sw_if_index;
   int filter;
 } vnet_pcap_dispatch_trace_args_t;
diff --git a/src/vnet/interface_cli.c b/src/vnet/interface_cli.c
index c62a9858e8c..531710fd5ad 100644
--- a/src/vnet/interface_cli.c
+++ b/src/vnet/interface_cli.c
@@ -1973,15 +1973,25 @@ vnet_pcap_dispatch_trace_configure (vnet_pcap_dispatch_trace_args_t * a)
 
   if (a->rx_enable + a->tx_enable + a->drop_enable)
     {
+      void *save_pcap_data;
+
       /* Sanity check max bytes per pkt */
       if (a->max_bytes_per_pkt < 32 || a->max_bytes_per_pkt > 9000)
 	return VNET_API_ERROR_INVALID_MEMORY_SIZE;
 
       /* Clean up from previous run, if any */
-      vec_free (pm->file_name);
-      vec_free (pm->pcap_data);
+      vec_reset_length (pm->pcap_data);
+
+      /* Throw away the data buffer? */
+      if (a->free_data)
+	vec_free (pm->pcap_data);
+
+      save_pcap_data = pm->pcap_data;
+
       memset (pm, 0, sizeof (*pm));
 
+      pm->pcap_data = save_pcap_data;
+
       vec_validate_aligned (vnet_trace_dummy, 2048, CLIB_CACHE_LINE_BYTES);
       if (pm->lock == 0)
 	clib_spinlock_init (&(pm->lock));
@@ -2003,6 +2013,14 @@ vnet_pcap_dispatch_trace_configure (vnet_pcap_dispatch_trace_args_t * a)
       pm->file_name = (char *) a->filename;
       pm->n_packets_captured = 0;
       pm->packet_type = PCAP_PACKET_TYPE_ethernet;
+      /* Preallocate the data vector? */
+      if (a->preallocate_data)
+	{
+	  vec_validate
+	    (pm->pcap_data, a->packets_to_capture
+	     * ((sizeof (pcap_packet_header_t) + a->max_bytes_per_pkt)));
+	  vec_reset_length (pm->pcap_data);
+	}
       pm->n_packets_to_capture = a->packets_to_capture;
       pp->pcap_sw_if_index = a->sw_if_index;
       if (a->filter)
@@ -2035,6 +2053,9 @@ vnet_pcap_dispatch_trace_configure (vnet_pcap_dispatch_trace_args_t * a)
 	      clib_error_report (error);
 	      return VNET_API_ERROR_SYSCALL_ERROR_1;
 	    }
+	  vec_free (pm->file_name);
+	  if (a->free_data)
+	    vec_free (pm->pcap_data);
 	  return 0;
 	}
       else
@@ -2057,9 +2078,11 @@ pcap_trace_command_fn (vlib_main_t * vm,
   int rv;
   int rx_enable = 0;
   int tx_enable = 0;
+  int preallocate_data = 0;
   int drop_enable = 0;
   int status = 0;
   int filter = 0;
+  int free_data = 0;
   u32 sw_if_index = 0;		/* default: any interface */
 
   /* Get a line of input. */
@@ -2091,7 +2114,16 @@ pcap_trace_command_fn (vlib_main_t * vm,
       else if (unformat (line_input, "intfc %U",
 			 unformat_vnet_sw_interface, vnm, &sw_if_index))
 	;
-      else if (unformat (line_input, "intfc any"))
+      else if (unformat (line_input, "interface %U",
+			 unformat_vnet_sw_interface, vnm, &sw_if_index))
+	;
+      else if (unformat (line_input, "preallocate-data %=",
+			 &preallocate_data, 1))
+	;
+      else if (unformat (line_input, "free-data %=", &free_data, 1))
+	;
+      else if (unformat (line_input, "intfc any")
+	       || unformat (line_input, "interface any"))
 	sw_if_index = 0;
       else if (unformat (line_input, "filter"))
 	filter = 1;
@@ -2108,6 +2140,8 @@ pcap_trace_command_fn (vlib_main_t * vm,
   a->filename = filename;
   a->rx_enable = rx_enable;
   a->tx_enable = tx_enable;
+  a->preallocate_data = preallocate_data;
+  a->free_data = free_data;
   a->drop_enable = drop_enable;
   a->status = status;
   a->packets_to_capture = max;
@@ -2177,6 +2211,12 @@ pcap_trace_command_fn (vlib_main_t * vm,
  * - <b>max-bytes-per-pkt <nnnn></b> - Maximum number of bytes to capture
  *   for each packet. Must be >= 32, <= 9000.
  *
+ * - <b>preallocate-data</b> - Preallocate the data buffer, to avoid
+ *   vector expansion delays during pcap capture
+ *
+ * - <b>free-data</b> - Free the data buffer. Ordinarily it's a feature
+ *   to retain the data buffer so this option is seldom used.
+ *
  * - <b>intfc <interface-name>|any</b> - Used to specify a given interface,
  *   or use '<em>any</em>' to run packet capture on all interfaces.
  *   '<em>any</em>' is the default if not provided. Settings from a previous
@@ -2226,7 +2266,9 @@ pcap_trace_command_fn (vlib_main_t * vm,
 VLIB_CLI_COMMAND (pcap_tx_trace_command, static) = {
     .path = "pcap trace",
     .short_help =
-    "pcap trace rx tx drop off [max <nn>] [intfc <interface>|any] [file <name>] [status] [max-bytes-per-pkt <nnnn>][filter]",
+    "pcap trace [rx] [tx] [drop] [off] [max <nn>] [intfc <interface>|any]\n"
+    "           [file <name>] [status] [max-bytes-per-pkt <nnnn>][filter]\n"
+    "           [preallocate-data][free-data]",
     .function = pcap_trace_command_fn,
 };
 /* *INDENT-ON* */