netdev - [PATCH] af_packet: fix efficiency issues in packet_read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220406114807.1803-1-lianglixue@greatwall.com.cn>
Date:   Wed,  6 Apr 2022 11:48:07 +0000
From:   lianglixue <lixue.liang5086@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com
Cc:     edumazet@...gle.com, pablo@...filter.org, rsanger@...d.net.nz,
        yajun.deng@...ux.dev, jiapeng.chong@...ux.alibaba.com,
        netdev@...r.kernel.org, lianglixue <lianglixue@...atwall.com.cn>
Subject: [PATCH] af_packet: fix efficiency issues in packet_read_pending

In packet_read_pengding, even if the pending_refcnt of the first CPU
is not 0, the pending_refcnt of all CPUs will be traversed,
and the long delay of cross-cpu access in NUMA significantly reduces
the performance of packet sending; especially in tpacket_destruct_skb.

When pending_refcnt is not 0, it returns without counting the number of
all pending packets, which significantly reduces the traversal time.

Signed-off-by: lianglixue <lianglixue@...atwall.com.cn>
---
 net/packet/af_packet.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c39c09899fd0..c04f49e44a33 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1210,17 +1210,18 @@ static void packet_dec_pending(struct packet_ring_buffer *rb)
 
 static unsigned int packet_read_pending(const struct packet_ring_buffer *rb)
 {
-	unsigned int refcnt = 0;
 	int cpu;
 
 	/* We don't use pending refcount in rx_ring. */
 	if (rb->pending_refcnt == NULL)
 		return 0;
 
-	for_each_possible_cpu(cpu)
-		refcnt += *per_cpu_ptr(rb->pending_refcnt, cpu);
+	for_each_possible_cpu(cpu) {
+		if (*per_cpu_ptr(rb->pending_refcnt, cpu) != 0)
+			return 1;
+	}
 
-	return refcnt;
+	return 0;
 }
 
 static int packet_alloc_pending(struct packet_sock *po)
-- 
2.27.0