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Subject[PATCH net-next] net: snmp: add statistics for tcp small queue check
Date
From: Menglong Dong <imagedong@tencent.com>

Once tcp small queue check failed in tcp_small_queue_check(), the
throughput of tcp will be limited, and it's hard to distinguish
whether it is out of tcp congestion control.

Add statistics of LINUX_MIB_TCPSMALLQUEUEFAILURE for this scene.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
include/uapi/linux/snmp.h | 1 +
net/ipv4/proc.c | 1 +
net/ipv4/tcp_output.c | 5 ++++-
3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 904909d020e2..e32ec6932e82 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -292,6 +292,7 @@ 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 f30273afb539..43b7a77cd6b4 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -297,6 +297,7 @@ 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 2e6e5a70168e..5b978c402eb4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2524,8 +2524,11 @@ 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)
+ if (refcount_read(&sk->sk_wmem_alloc) > limit) {
+ __NET_INC_STATS(sock_net(sk),
+ LINUX_MIB_TCPSMALLQUEUEFAILURE);
return true;
+ }
}
return false;
}
--
2.27.0
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