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Message-Id: <1423115891-3578-1-git-send-email-al.drozdov@gmail.com> Date: Thu, 5 Feb 2015 08:58:11 +0300 From: Alexander Drozdov <al.drozdov@...il.com> To: "David S. Miller" <davem@...emloft.net> Cc: Daniel Borkmann <dborkman@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Al Viro <viro@...iv.linux.org.uk>, Willem de Bruijn <willemb@...gle.com>, "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Alexander Drozdov <al.drozdov@...il.com> Subject: [PATCH] af_packet: don't pass empty blocks for PACKET_V3 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.drozdov@...il.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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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