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

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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>
This commit is contained in:
Eric Dumazet 2021-11-30 19:32:46 -08:00 committed by Jakub Kicinski
parent 0dc1df0598
commit ce8299b6f7
3 changed files with 1 additions and 6 deletions
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1
include/uapi/linux/snmp.h
View File

@ -292,7 +292,6 @@ enum
LINUX_MIB_TCPDSACKIGNOREDDUBIOUS, /* TCPDSACKIgnoredDubious */
LINUX_MIB_TCPMIGRATEREQSUCCESS, /* TCPMigrateReqSuccess */
LINUX_MIB_TCPMIGRATEREQFAILURE, /* TCPMigrateReqFailure */
LINUX_MIB_TCPSMALLQUEUEFAILURE, /* TCPSmallQueueFailure */
__LINUX_MIB_MAX
};

1
net/ipv4/proc.c
View File

@ -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
};

5
net/ipv4/tcp_output.c
View File

@ -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;
}