[Freeswitch-dev] On high CPU usage and NONBLOCK-ed sockets

[Mathieu Parent]

On Fri, Sep 3, 2010 at 8:22 PM, Anthony Minessale
<anthony.minessale at gmail.com> wrote:
> What do you mean by high cpu exactly?
when going blocking-mode, the user CPU gets lower and the kernel CPU is similar.

>  what are you using to measure it?
top, vmstat

without mod_skinny
mathieu at netthieu:~/apps/freeswitch/freeswitch.git$ vmstat 5 5
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 7  0     48 175552 161664 787636    0    0     8    10  184  361  6  8 86  1
 1  0     48 171948 161672 791372    0    0     0     5 4141 9191 14 12 74  0
 0  0     48 171700 161684 791496    0    0     0    11 4125 9081 13  9 78  0
 0  0     48 175048 161688 787860    0    0     0     3 4344 9177  7 10 84  0
 6  0     48 175048 161692 787860    0    0     0     1 4225 9035  9 11 80  0

with mod_skinny NONBLOCKED
mathieu at netthieu:~/apps/freeswitch/freeswitch.git$ vmstat 5 5
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1  0     48 172668 162104 789052    0    0     8    10  190  374  6  8 86  1
 1  0     48 173528 162108 788652    0    0     0     2 4792 10346 15 13 72  0
 1  0     48 173528 162124 788664    0    0     0    17 4678 10326  9 12 78  0
 0  0     48 173528 162124 788628    0    0     0     1 4788 10343 10 14 77  0
 9  0     48 166956 162136 792764    0    0     0    10 4592 10535 16 13 71  0

with mod_skinny BLOCKED
mathieu at netthieu:~/apps/freeswitch/freeswitch.git$ vmstat 5 5
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0     48 175288 161648 787832    0    0     8    10  182  358  6  8 86  1
 1  0     48 175280 161648 787824    0    0     0     0 4236 9054  7  9 83  0
 7  0     48 175404 161648 787804    0    0     0     3 4173 8927  7 10 83  0
 0  0     48 175280 161652 787576    0    0     0     5 4288 9182  9 10 81  0
 6  0     48 175404 161656 787580    0    0     0     4 4209 9001  8 10 82  0

So it seems that both %user and %system are lower. I have not done
complete tests but mod_skinny is more responsive in BLOCKING-mode

> what OS are you on?
Linux netthieu 2.6.32-5-686 #1 SMP Thu Aug 12 13:38:27 UTC 2010 i686 GNU/Linux

this is Debian testing using FS built from recent git using debian packaging.


> in my findings not more efficient, not at all reliable.
Googling some, I found (from
http://www.ibm.com/developerworks/linux/library/l-async/)

"Synchronous non-blocking I/O: A less efficient variant of synchronous
blocking". This is what we are doing?

The good solutions IMO are:
- Synchronous blocking I/O: simple and efficient
- Asynchronous blocking I/O: not so good. use of "select" is not recommended
- Asynchronous non-blocking I/O (AIO) which is a completely different
API (portable?) which should fit well with FS's event model but with a
lot of work

Maybe we can make it configurable at build-time (as it is in
mod_skinny) to allow performance testing? Perhaps the results will be
very different from one platform to another.

Mathieu