Very high CPU usage and very slow startup times


#1

A few weeks ago we started noticing some very bad performance on HAProxy restart, this is most likely due to a configuration issue on our side. I am not sure what it is. Essentially we notices that CPU goes to 100% for almost a minute on reload and stays that way for about a minute during which most sites are not responsive.

We are currently using HAProxy 1.5.15 we are hosting about ~50 SSL sites

Our basic stats are:

pid = 27365 (process #1, nbproc = 1)
uptime = 0d 1h39m22s
system limits: memmax = unlimited; ulimit-n = 100196
maxsock = 100196; maxconn = 50000; maxpipes = 0
current conns = 14149; current pipes = 0/0; conn rate = 352/sec
Running tasks: 3/14430; idle = 19 %

I tried to dig in with strace and noticed:

/etc/haproxy/ssl# strace -c -p 27365

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 16.38    0.039534           2     23576      1002 sendto
 12.39    0.029900           1     49156     13160 read
 12.33    0.029753           2     12506        47 write
 11.85    0.028598           2     14443           close
 11.29    0.027246           3      9123      9113 connect
  8.09    0.019521           1     16834           epoll_wait
  6.68    0.016115           1     25885     10521 recvfrom
  4.26    0.010281           1     18925           setsockopt
  4.26    0.010270           1     16549           epoll_ctl
  3.66    0.008839           2      5094         3 shutdown
  3.62    0.008737           1      9112           socket
  3.44    0.008313           1      9091      4219 accept4
  1.62    0.003922           0      9112           fcntl
  0.12    0.000285           0       655           getsockopt
  0.02    0.000044           1        47           brk
------ ----------- ----------- --------- --------- ----------------
100.00    0.241358                220108     38065 total

This seems normalish … but this feels a bit fishy

#strace -p 23815 2> trace.log
# cat trace.log  | wc
  38761  298182 3304312
# cat trace.log  | grep EAGAIN | wc
   4075   41099  366647

So we are seeing a nice 10% EAGAIN going on, which feels a bit on the high side:

read(7097, 0x19e0a063, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(4697, 0xb48cc53, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(1755, 0x995eac3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(7797, 0x11fc7693, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(7485, 0x16f89ea3, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(3150, 0x875e473, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(8061, 0x16f89ea3, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(4383, 0xae8b9e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(13587, 0x157239a4, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
read(4930, 0x9043523, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(8938, 0x19fd0943, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(8718, 0xae8b9e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(13380, 0x1c8184c4, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(10747, 0x21d08de4, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(15751, 0xa9dc2c4, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(7504, 0x25c75b4, 16384, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(509, 0x253db34, 16384, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(10997, 0x2579f74, 16384, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(5962, 0x259f2d4, 16384, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(8504, 0x25b3444, 16384, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
accept4(46, 0x7ffeef362560, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
read(1831, 0x39a6f83, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(1416, 0x994a8e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(1127, 0x3104fe60, 11)              = -1 EAGAIN (Resource temporarily unavailable)
accept4(44, 0x7ffeef362560, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
read(15685, 0x3042793, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(13465, 0xc18bf6b, 1177)            = -1 EAGAIN (Resource temporarily unavailable)
accept4(45, 0x7ffeef362560, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
read(13541, 0x11fc7693, 5)              = -1 EAGAIN (Resource temporarily unavailable)
read(5578, 0x994a8e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(4417, 0x994a8e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(15750, 0x26cc5a53, 5)              = -1 EAGAIN (Resource temporarily unavailable)
read(601, 0x11fc7693, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(9746, 0xae8b9e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(5593, 0x16f9e173, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(1525, 0x11fc7693, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(2083, 0x994a8e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(11021, 0x13b55954, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
read(2659, 0x23108db3, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(1806, 0x994a8e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(5717, 0xb48cc53, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(9391, 0x11fc7693, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(6639, 0xae8b9e3, 5)                = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(14023, 0x112bdb64, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(15683, 0x7b533c2, 4834, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
read(2535, 0xb48cc53, 5)                = -1 EAGAIN (Resource temporarily unavailable)
read(15519, 0x37aaa43, 5)               = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(15753, 0x87cc0a4, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(15721, 0xb4fd684, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
read(1620, 0x875e473, 5)                = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(15672, 0x295329ee, 7974, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvfrom(15675, 0x8dc2ed4, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
accept4(46, 0x7ffeef362560, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
read(3561, 0x1420d253, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(1353, 0x11fc7693, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(1015, 0x23108db0, 11)              = -1 EAGAIN (Resource temporarily unavailable)
accept4(44, 0x7ffeef362560, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
read(10787, 0x9043523, 5)               = -1 EAGAIN (Resource temporarily unavailable)
accept4(19, 0x7ffeef362560, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
read(7142, 0x9043523, 5)                = -1 EAGAIN (Resource temporarily unavailable)

Our CPU is running at 40-70% constantly on reload it runs at 100% for almost a minute.

We run a Xeon E5606 @ 2.13GHz

How should we go about cutting down on the CPU?

Upgrade to 1.6.2?

Offload SSL?

Split up our HAProxy instance?


#2

A few weeks ago we started noticing some very bad performance on HAProxy
restart, this is most likely due to a configuration issue on our side. I am
not sure what it is. Essentially we notices that CPU goes to 100% for almost
a minute on reload and stays that way for about a minute during which most
sites are not responsive.

Wow! I suspect that’s related to SSL because all your visitors are being
rekeyed. Let me guess, most of the time is spent in userland ?

We are currently using HAProxy 1.5.15 we are hosting about ~50 SSL sites

Our basic stats are:

pid = 27365 (process #1, nbproc = 1)
uptime = 0d 1h39m22s
system limits: memmax = unlimited; ulimit-n = 100196
maxsock = 100196; maxconn = 50000; maxpipes = 0
current conns = 14149; current pipes = 0/0; conn rate = 352/sec
Running tasks: 3/14430; idle = 19 %

I tried to dig in with strace and noticed:

/etc/haproxy/ssl# strace -c -p 27365

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 16.38    0.039534           2     23576      1002 sendto
 12.39    0.029900           1     49156     13160 read
 12.33    0.029753           2     12506        47 write
 11.85    0.028598           2     14443           close
 11.29    0.027246           3      9123      9113 connect
  8.09    0.019521           1     16834           epoll_wait
  6.68    0.016115           1     25885     10521 recvfrom
  4.26    0.010281           1     18925           setsockopt
  4.26    0.010270           1     16549           epoll_ctl
  3.66    0.008839           2      5094         3 shutdown
  3.62    0.008737           1      9112           socket
  3.44    0.008313           1      9091      4219 accept4
  1.62    0.003922           0      9112           fcntl
  0.12    0.000285           0       655           getsockopt
  0.02    0.000044           1        47           brk
------ ----------- ----------- --------- --------- ----------------
100.00    0.241358                220108     38065 total

This seems normalish … but this feels a bit fishy

#strace -p 23815 2> trace.log
# cat trace.log  | wc
  38761  298182 3304312
# cat trace.log  | grep EAGAIN | wc
   4075   41099  366647

So we are seeing a nice 10% EAGAIN going on, which feels a bit on the high side:

No that’s perfectly normal. read() represents about 20% of your syscalls
and bout half of them are the second ones which re-enable polling so that’s
indeed 10%.

read(7097, 0x19e0a063, 5)               = -1 EAGAIN (Resource temporarily unavailable)
read(4697, 0xb48cc53, 5)                = -1 EAGAIN (Resource temporarily unavailable)

(…)

Our CPU is running at 40-70% constantly on reload it runs at 100% for almost a minute.

The simple fact that above we see more read() than recvfrom() indicates
you’re doing a lot of SSL (only openssl does read()).

We run a Xeon E5606 @ 2.13GHz

How should we go about cutting down on the CPU?

Upgrade to 1.6.2?

Offload SSL?

Split up our HAProxy instance?

With 1.6 you have the ability to reuse your TLS tickets’ secret across
processes, so if your clients support TLS tickets (ie almost all clients)
then sessions will not be renegociated upon reload. It will even support
sharing the secrets between multiple LB nodes.

If you find that you manipulate the HTTP part of the config a lot and
very rarely the SSL part, it could also make sense to split the config
to have just an off-loading instance first and the regular one behind,
but I’d rather try the secrets sharing first to make things easier.
Please have a look at “tls-ticket-keys” in the doc.


#5

Is the nbprocs something you would recommend for better spreading the load across cores? we have a lot of cores doing nothing while one core is permanently at 50%-70%


#6

Definitely. However keep in mind that some information are not shared between processes (stick-tables, health-checks, stats) so it tends to become a bit more complex to manage. Since you’re doing a lot of SSL, a good approach often consists in dedicating several processes to SSL offloading only and to pass the traffic to a single-process instance. This way you get the best of both worlds. Example with process 1 for clear text, and processes 2…N for SSL only :

listen offload
      mode tcp
      bind :443 ssl crt blah.pem ... process 2
      bind :443 ssl crt blah.pem ... process 3
      ...
      server clear 127.0.0.1:81 send-proxy-v2

frontend clear
      mode http
      bind-process 1
      bind :80 name http
      bind :81 accept-proxy name ssl-offload
      ...