pktgen: add flag NO_TIMESTAMP to disable timestamping

Then testing the TX limits of the stack, then it is useful to
be-able to disable the do_gettimeofday() timetamping on every packet.

This implements a pktgen flag NO_TIMESTAMP which will disable this
call to do_gettimeofday().

The performance change on (my system E5-2695) with skb_clone=0, goes
from TX 2,423,751 pps to 2,567,165 pps with flag NO_TIMESTAMP. Thus,
the cost of do_gettimeofday() or saving is approx 23 nanosec.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 3 deletions

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 5b36a9428c59..21cb4839bc97 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -202,6 +202,7 @@
 #define F_QUEUE_MAP_CPU (1<<14) /* queue map mirrors smp_processor_id() */
 #define F_NODE          (1<<15) /* Node memory alloc*/
 #define F_UDPCSUM       (1<<16) /* Include UDP checksum */
+#define F_NO_TIMESTAMP  (1<<17) /* Don't timestamp packets (default TS) */
 
 /* Thread control flag bits */
 #define T_STOP        (1<<0)    /* Stop run */
@@ -638,6 +639,9 @@ static int pktgen_if_show(struct seq_file *seq, void *v)
         if (pkt_dev->flags & F_UDPCSUM)
                 seq_puts(seq, "UDPCSUM  ");
 
+        if (pkt_dev->flags & F_NO_TIMESTAMP)
+                seq_puts(seq, "NO_TIMESTAMP  ");
+
         if (pkt_dev->flags & F_MPLS_RND)
                 seq_puts(seq,  "MPLS_RND  ");
 
@@ -1243,6 +1247,9 @@ static ssize_t pktgen_if_write(struct file *file,
                 else if (strcmp(f, "!UDPCSUM") == 0)
                         pkt_dev->flags &= ~F_UDPCSUM;
 
+                else if (strcmp(f, "NO_TIMESTAMP") == 0)
+                        pkt_dev->flags |= F_NO_TIMESTAMP;
+
                 else {
                         sprintf(pg_result,
                                 "Flag -:%s:- unknown\nAvailable flags, (prepend ! to un-set flag):\n%s",
@@ -1251,6 +1258,7 @@ static ssize_t pktgen_if_write(struct file *file,
                                 "MACSRC_RND, MACDST_RND, TXSIZE_RND, IPV6, "
                                 "MPLS_RND, VID_RND, SVID_RND, FLOW_SEQ, "
                                 "QUEUE_MAP_RND, QUEUE_MAP_CPU, UDPCSUM, "
+                                "NO_TIMESTAMP, "
 #ifdef CONFIG_XFRM
                                 "IPSEC, "
 #endif
@@ -2685,9 +2693,14 @@ static void pktgen_finalize_skb(struct pktgen_dev *pkt_dev, struct sk_buff *skb,
         pgh->pgh_magic = htonl(PKTGEN_MAGIC);
         pgh->seq_num = htonl(pkt_dev->seq_num);
 
-        do_gettimeofday(&timestamp);
-        pgh->tv_sec = htonl(timestamp.tv_sec);
-        pgh->tv_usec = htonl(timestamp.tv_usec);
+        if (pkt_dev->flags & F_NO_TIMESTAMP) {
+                pgh->tv_sec = 0;
+                pgh->tv_usec = 0;
+        } else {
+                do_gettimeofday(&timestamp);
+                pgh->tv_sec = htonl(timestamp.tv_sec);
+                pgh->tv_usec = htonl(timestamp.tv_usec);
+        }
 }
 
 static struct sk_buff *pktgen_alloc_skb(struct net_device *dev,