Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751466AbbBEF7K (ORCPT ); Thu, 5 Feb 2015 00:59:10 -0500 Received: from mail-la0-f47.google.com ([209.85.215.47]:65447 "EHLO mail-la0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751026AbbBEF7I (ORCPT ); Thu, 5 Feb 2015 00:59:08 -0500 From: Alexander Drozdov To: "David S. Miller" Cc: Daniel Borkmann , Eric Dumazet , Al Viro , Willem de Bruijn , "Michael S. Tsirkin" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Drozdov Subject: [PATCH] af_packet: don't pass empty blocks for PACKET_V3 Date: Thu, 5 Feb 2015 08:58:11 +0300 Message-Id: <1423115891-3578-1-git-send-email-al.drozdov@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1851 Lines: 51 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 --- 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 linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/