Revert "net: snmp: add statistics for tcp small queue check"

This reverts commit aeeecb889165617a841e939117f9a8095d0e7d80.

The new SNMP variable (TCPSmallQueueFailure) can be incremented
for good reasons, even on a 100Gbit single TCP_STREAM flow.

If we really wanted to ease driver debugging [1], this would
require something more sophisticated.

[1] Usually, if a driver is delaying TX completions too much,
this can lead to stalls in TCP output. Various work arounds
have been used in the past, like skb_orphan() in ndo_start_xmit().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Menglong Dong <imagedong@tencent.com>
Link: https://lore.kernel.org/r/20211201033246.2826224-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index e32ec69..904909d 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -292,7 +292,6 @@ enum
        LINUX_MIB_TCPDSACKIGNOREDDUBIOUS,       /* TCPDSACKIgnoredDubious */
        LINUX_MIB_TCPMIGRATEREQSUCCESS,         /* TCPMigrateReqSuccess */
        LINUX_MIB_TCPMIGRATEREQFAILURE,         /* TCPMigrateReqFailure */
-       LINUX_MIB_TCPSMALLQUEUEFAILURE,         /* TCPSmallQueueFailure */
        __LINUX_MIB_MAX
 };
 

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 43b7a77..f30273a 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -297,7 +297,6 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TCPDSACKIgnoredDubious", LINUX_MIB_TCPDSACKIGNOREDDUBIOUS),
        SNMP_MIB_ITEM("TCPMigrateReqSuccess", LINUX_MIB_TCPMIGRATEREQSUCCESS),
        SNMP_MIB_ITEM("TCPMigrateReqFailure", LINUX_MIB_TCPMIGRATEREQFAILURE),
-       SNMP_MIB_ITEM("TCPSmallQueueFailure", LINUX_MIB_TCPSMALLQUEUEFAILURE),
        SNMP_MIB_SENTINEL
 };
 

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index c4ab6c8..5079832 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2524,11 +2524,8 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
                 * test again the condition.
                 */
                smp_mb__after_atomic();
-               if (refcount_read(&sk->sk_wmem_alloc) > limit) {
-                       NET_INC_STATS(sock_net(sk),
-                                     LINUX_MIB_TCPSMALLQUEUEFAILURE);
+               if (refcount_read(&sk->sk_wmem_alloc) > limit)
                        return true;
-               }
        }
        return false;
 }