Bug 211375

Summary: Memory leak about TCP slab which have too big used sockets
Product: Networking Reporter: bianmingkun (390231410@qq.com)
Component: IPV4Assignee: Stephen Hemminger (stephen)
Status: NEEDINFO ---    
Severity: normal    
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 4.18.16 Subsystem:
Regression: No Bisected commit-id:

Description bianmingkun@gmail.com 2021-01-27 01:48:33 UTC 
Memory leak occurred in linux of 4.18.16, we use nginx as a server, I found some problems related to TCP as following:
1. slabtop a:
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
14081971 13980986 99% 2.06K 938799 15 30041568K TCP

2. cat /proc/meminfo
SUnreclaim: 31405028 kB

3. cat /proc/net/sockstat
sockets: used 13976123
TCP: inuse 18 orphan 0 tw 44 alloc 18 mem 1
UDP: inuse 54 mem 45
UDPLITE: inuse 0 RAW: inuse 9
FRAG: inuse 0 memory 0

4. lsof
there are 19000 line, it seems like ok.

As above, it seems that tcp sk memory leak, "sockets: used 13976123" illustrate that "net->core.sock_inuse" is too big, which increase in inet_create(socket create) or sk_clone_lock(child socket create) and decrease in __sk_free, I kill almost all of application layer program, but the "sockets: used" almostly not reduce.

Do you have any suggestions for this problem, Thanks.
Comment 1 Stephen Hemminger 2021-01-28 16:31:28 UTC 
That kernel version is end of live in two years ago.
Please reproduce with a supported kernel version.

A good choice would be 4.19.170 which the 19th LTS release.
This kernel will be supported until 2024