This is a note to let you know that I've just added the patch titled
af_packet: do not call packet_read_pending() from tpacket_destruct_skb()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
af_packet-do-not-call-packet_read_pending-from-tpack.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8a301e284547338e8bce1410d6a61b5899cd0ab6
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Wed May 15 16:33:58 2024 +0000
af_packet: do not call packet_read_pending() from tpacket_destruct_skb()
[ Upstream commit 581073f626e387d3e7eed55c48c8495584ead7ba ]
trafgen performance considerably sank on hosts with many cores
after the blamed commit.
packet_read_pending() is very expensive, and calling it
in af_packet fast path defeats Daniel intent in commit
b013840810c2 ("packet: use percpu mmap tx frame pending refcount")
tpacket_destruct_skb() makes room for one packet, we can immediately
wakeup a producer, no need to completely drain the tx ring.
Fixes: 89ed5b519004 ("af_packet: Block execution of tasks waiting for transmit to complete in AF_PACKET")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240515163358.4105915-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e8b05769d1c9a..4ddc60c7509fb 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2441,8 +2441,7 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
ts = __packet_set_timestamp(po, ph, skb);
__packet_set_status(po, ph, TP_STATUS_AVAILABLE | ts);
- if (!packet_read_pending(&po->tx_ring))
- complete(&po->skb_completion);
+ complete(&po->skb_completion);
}
sock_wfree(skb);
