Don't close an empty block on timeout. Its meaningless to
pass it to the user. Moreover, passing empty blocks wastes
CPU & buffer space increasing probability of packets
dropping on small timeouts.
Side effect of this patch is indefinite user-space wait
in poll on idle links. But, I believe its better to set
timeout for poll(2) when needed than to get empty blocks
every millisecond when not needed.
Signed-off-by: Alexander Drozdov <al.droz...@gmail.com>
---
net/packet/af_packet.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9cfe2e1..9a2f70a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -698,6 +698,10 @@ static void prb_retire_rx_blk_timer_expired(unsigned long
data)
if (pkc->last_kactive_blk_num == pkc->kactive_blk_num) {
if (!frozen) {
+ if (!BLOCK_NUM_PKTS(pbd)) {
+ /* An empty block. Just refresh the timer. */
+ goto refresh_timer;
+ }
prb_retire_current_block(pkc, po, TP_STATUS_BLK_TMO);
if (!prb_dispatch_next_block(pkc, po))
goto refresh_timer;
@@ -798,7 +802,11 @@ static void prb_close_block(struct tpacket_kbdq_core *pkc1,
h1->ts_last_pkt.ts_sec = last_pkt->tp_sec;
h1->ts_last_pkt.ts_nsec = last_pkt->tp_nsec;
} else {
- /* Ok, we tmo'd - so get the current time */
+ /* Ok, we tmo'd - so get the current time.
+ *
+ * It shouldn't really happen as we don't close empty
+ * blocks. See prb_retire_rx_blk_timer_expired().
+ */
struct timespec ts;
getnstimeofday(&ts);
h1->ts_last_pkt.ts_sec = ts.tv_sec;
--
1.9.1
--
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