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Re: high cpu load with tcpdump



On Mon, 29 Feb 2016, Christos Zoulas wrote:

| Hello,
|
| the problem occurs only on one of my servers. I tried to find the
| difference. It is the bind9 (bind-9.10.3pl3). If I stop the bind9, tcpdump
| works without problems. When I restart the bind9, the CPU load goes back
| to 100%.
|
| Is it a problem of the kernel, tcpdump or bind9?

Can you ktrace the bind? Perhaps it is waking up tcpdump spuriously.
That would indicate a kernel problem.

ktrace tcpdump starting at timestamp 1456773618

  1847      1 tcpdump  1456773617.999999648 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000001813 RET   read -1 errno 35 Resource temporarily unavailable
  1847      1 tcpdump  1456773618.000003699 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000006213 RET   read -1 errno 35 Resource temporarily unavailable
  1847      1 tcpdump  1456773618.000008029 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000010333 RET   read -1 errno 35 Resource temporarily unavailable
  1847      1 tcpdump  1456773618.000012289 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000015641 RET   read -1 errno 35 Resource temporarily unavailable
  1847      1 tcpdump  1456773618.000017667 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000020111 RET   read -1 errno 35 Resource temporarily unavailable
  1847      1 tcpdump  1456773618.000022206 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000024860 RET   read -1 errno 35 Resource temporarily unavailable
  1847      1 tcpdump  1456773618.000026746 CALL  read(3,0x7f7ff7b16000,0x80000)
  1847      1 tcpdump  1456773618.000028981 RET   read -1 errno 35 Resource temporarily unavailable
...


ktrace named starting at timestamp 1456773618

  2362      9 named    1456773617.648034355 CALL  setsockopt(0x262,0xffff,0x800,0x7f7ff09f8484,4)
  2362      6 named    1456773618.151726698 RET   setsockopt 0
  2362      6 named    1456773618.151732844 CALL  setsockopt(0x260,0xffff,0x2000,0x7f7ff15fb484,4)
  2362      3 named    1456773618.151748627 RET   setsockopt 0
  2362      6 named    1456773618.151749815 RET   setsockopt 0
  2362      3 named    1456773618.151760291 CALL  getsockopt(0x261,0xffff,0x1002,0x7f7ff21fe43c,0x7f7ff21fe438)
  2362      6 named    1456773618.151763224 CALL  getsockopt(0x260,0xffff,0x1002,0x7f7ff15fb48c,0x7f7ff15fb488)
  2362      9 named    1456773618.151783617 RET   setsockopt 0
  2362      3 named    1456773618.151790601 RET   getsockopt 0
  2362      6 named    1456773618.151792696 RET   getsockopt 0
  2362      5 named    1456773618.151793395 RET   __socket30 14/0xe
  2362      3 named    1456773618.151807642 CALL  bind(0x261,0x7f7ff21fe630,0x10)
  2362      5 named    1456773618.151812601 CALL  fcntl(0xe,0,0x200)
  2362      9 named    1456773618.151791509 CALL  setsockopt(0x262,0xffff,0x2000,0x7f7ff09f8484,4)
  2362      3 named    1456773618.151817071 MISC  mbsoname: [0.0.0.0]
  2362      6 named    1456773618.151803941 CALL  bind(0x260,0x7f7ff15fb680,0x10)
  2362      6 named    1456773618.151832016 MISC  mbsoname: [0.0.0.0]
  2362      3 named    1456773618.151861768 RET   bind 0
  2362      5 named    1456773618.151883279 RET   fcntl 611/0x263
  2362      3 named    1456773618.151884815 CALL  recvmsg(0x261,0x7f7ff21fe320,0)
  2362      5 named    1456773618.151889844 CALL  close(0xe)
  2362      3 named    1456773618.151893545 MISC  msghdr: [name=0x7f7fef511088, namelen=128, iov=0x7f7ff21fe350, iovlen=1, control=0x7f7ff39a6fa0, controllen=96, flags=4000000]
  2362      5 named    1456773618.151908980 RET   close 0
  2362      5 named    1456773618.151913729 CALL  fcntl(0x263,3,0)
  2362      5 named    1456773618.151916732 RET   fcntl 2
  2362      5 named    1456773618.151920992 CALL  fcntl(0x263,4,6)
  2362      9 named    1456773618.151922808 RET   setsockopt 0
  2362      9 named    1456773618.151943900 CALL  getsockopt(0x262,0xffff,0x1002,0x7f7ff09f848c,0x7f7ff09f8488)
  2362      9 named    1456773618.151980705 RET   getsockopt 0
  2362      9 named    1456773618.151992299 CALL  bind(0x262,0x7f7ff09f8680,0x10)
  2362      9 named    1456773618.152000051 MISC  mbsoname: [0.0.0.0]
  2362     11 named    1456773618.152002845 RET   close 0
  2362     11 named    1456773618.152016184 CALL  read(5,0x7f7ff01f6f10,8)
  2362      9 named    1456773618.152018768 RET   bind 0
  2362      6 named    1456773618.152018140 RET   bind 0
  2362      3 named    1456773618.152029244 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362     11 named    1456773618.152035390 GIO   fd 5 read 8 bytes ",\^B\0\0\M-{\M^?\M^?\M^?"
  2362     11 named    1456773618.152041396 RET   read 8
  2362      6 named    1456773618.152040698 CALL  recvmsg(0x260,0x7f7ff15fb370,0)
  2362      9 named    1456773618.152033854 CALL  recvmsg(0x262,0x7f7ff09f8370,0)
  2362     11 named    1456773618.152050266 CALL  __kevent50(8,0x7f7ff01f6f20,1,0,0,0)
  2362      9 named    1456773618.152061650 MISC  msghdr: [name=0x7f7fef50f328, namelen=128, iov=0x7f7ff09f83a0, iovlen=1, control=0x7f7ff3d98fa0, controllen=96, flags=4000000]
  2362      6 named    1456773618.152051663 MISC  msghdr: [name=0x7f7fef517088, namelen=128, iov=0x7f7ff15fb3a0, iovlen=1, control=0x7f7fec6ca1e0, controllen=96, flags=4000000]
  2362      3 named    1456773618.152041047 CALL  write(7,0x7f7ff21fe3e0,8)
  2362     11 named    1456773618.152075688 RET   __kevent50 -1 errno 2 No such file or directory
  2362      9 named    1456773618.152081694 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      6 named    1456773618.152085116 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      9 named    1456773618.152089586 CALL  write(7,0x7f7ff09f8430,8)
  2362      6 named    1456773618.152093986 CALL  write(7,0x7f7ff15fb430,8)
  2362     11 named    1456773618.152082322 CALL  __kevent50(8,0x7f7ff01f6f20,1,0,0,0)
  2362      9 named    1456773618.152102087 GIO   fd 7 wrote 8 bytes "b\^B\0\0\M-}\M^?\M^?\M^?"
  2362      6 named    1456773618.152106976 GIO   fd 7 wrote 8 bytes "`\^B\0\0\M-}\M^?\M^?\M^?"
  2362      3 named    1456773618.152084837 GIO   fd 7 wrote 8 bytes "a\^B\0\0\M-}\M^?\M^?\M^?"
  2362     11 named    1456773618.152107674 RET   __kevent50 -1 errno 2 No such file or directory
  2362      3 named    1456773618.152118150 RET   write 8
...

maybe interesting:

kdump -T -f bind.ktrace | grep temporarily
...
  2362      7 named    1456773591.659648856 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      3 named    1456773591.659831278 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362     11 named    1456773591.659937993 RET   read -1 errno 35 Resource temporarily unavailable
  2362      3 named    1456773591.660328049 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362     11 named    1456773591.660407666 RET   read -1 errno 35 Resource temporarily unavailable
  2362     11 named    1456773591.660658950 RET   read -1 errno 35 Resource temporarily unavailable
...
  2362      3 named    1456773618.152029244 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      9 named    1456773618.152081694 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      6 named    1456773618.152085116 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      8 named    1456773618.656240078 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      6 named    1456773618.656509381 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      9 named    1456773618.656578243 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      7 named    1456773618.657299200 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      3 named    1456773618.657380703 RET   recvmsg -1 errno 35 Resource temporarily unavailable
  2362      9 named    1456773618.790215928 RET   recvmsg -1 errno 35 Resource temporarily unavailable


Any Ideas?


Regards
Uwe


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