haproxy/tests/io_limits.txt

---------- epoll without limits --------
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 47.19    2.671077          56     48093     22397 recv
 47.15    2.668840         106     25060      4858 send
  2.19    0.124020          10     12150           epoll_ctl
  1.96    0.110904         286       388           epoll_wait
  0.56    0.031565          47       670           close
  0.19    0.010481          28       380       350 connect
  0.15    0.008650          25       350           socket
  0.14    0.008204          26       320           shutdown
  0.14    0.007655          22       355        35 accept
  0.12    0.006871          10       670           setsockopt
  0.11    0.006194           9       670           fcntl64
  0.07    0.004148          12       355           brk
  0.04    0.002055           5       389           gettimeofday
------ ----------- ----------- --------- --------- ----------------
100.00    5.660664                 89850     27640 total


---------- sepoll without limit --------
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 49.43    2.770682          97     28486      3861 send
 46.48    2.605336          53     49317     23434 recv
  2.00    0.111916         206       542           epoll_wait
  0.65    0.036325          12      3030           epoll_ctl
  0.45    0.025282          38       670           close
  0.24    0.013247          34       388       358 connect
  0.17    0.009544          27       350           socket
  0.16    0.008734          27       320           shutdown
  0.11    0.006432          18       357        37 accept
  0.10    0.005699           9       670           setsockopt
  0.08    0.004724           7       670           fcntl64
  0.08    0.004568           6       767           gettimeofday
  0.06    0.003127           9       356           brk
------ ----------- ----------- --------- --------- ----------------
100.00    5.605616                 85923     27690 total


---------- sepoll with send limit only --------
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 49.21    2.779349         109     25417       418 send
 46.94    2.651058          54     49150     23368 recv
  1.77    0.099863         264       378           epoll_wait
  0.57    0.032141          14      2351           epoll_ctl
  0.46    0.025822          39       670           close
  0.25    0.014300          37       387       357 connect
  0.19    0.010530          30       350           socket
  0.15    0.008656          27       320           shutdown
  0.14    0.008008          23       354        34 accept
  0.11    0.006051           9       670           setsockopt
  0.10    0.005461           8       670           fcntl64
  0.07    0.003842           6       604           gettimeofday
  0.06    0.003120           9       358           brk
------ ----------- ----------- --------- --------- ----------------
100.00    5.648201                 81679     24177 total


---------- sepoll with send + recv limits --------
Process 3173 attached - interrupt to quit
Process 3173 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 49.09    2.802918         105     26771       596 send
 47.72    2.724651          89     30761       728 recv
  1.12    0.063952          55      1169           epoll_wait
  0.47    0.026810          40       676           close
  0.44    0.025358          11      2329           epoll_ctl
  0.21    0.012255          30       403       367 connect
  0.20    0.011135          35       320           shutdown
  0.18    0.010313          29       356           socket
  0.15    0.008614           6      1351           gettimeofday
  0.13    0.007678          21       360        40 accept
  0.13    0.007218          11       676           setsockopt
  0.10    0.005559           8       676           fcntl64
  0.05    0.002882           9       327           brk
------ ----------- ----------- --------- --------- ----------------
100.00    5.709343                 66175      1731 total

---------- epoll with send+recv limits -----------
Process 3271 attached - interrupt to quit
Process 3271 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 46.96    2.742476         124     22193           send
 46.55    2.718027          98     27730           recv
  2.58    0.150701          11     13331           epoll_ctl
  2.30    0.134350         135       998           epoll_wait
  0.52    0.030520          45       673           close
  0.23    0.013422          42       320           shutdown
  0.19    0.011282          29       386       353 connect
  0.19    0.011063          31       353           socket
  0.12    0.007039          20       359        39 accept
  0.11    0.006629          10       673           fcntl64
  0.10    0.005920           9       673           setsockopt
  0.09    0.005157           5       999           gettimeofday
  0.05    0.002885           9       335           brk
------ ----------- ----------- --------- --------- ----------------
100.00    5.839471                 69023       392 total


Conclusion
----------
epoll         = 89850 syscalls
sepoll        = 85923 syscalls
epoll+limits  = 69023 syscalls
sepoll+limits = 66175 syscalls

=> limits reduce the number of syscalls by 23%
=> sepoll reduces the number of syscalls by 4%
=> sepoll reduces the number of epoll_ctl by 83%
=> limits reduce the number of epoll_ctl by 24%
=> limits increase the number of epoll_wait by 115%