Re: tcpdump vs libpcap : CPU usage shooting high for two simultaneous captures on wireless monitor interfaces

[abhinav narain <abhinavnarain10 () gmail com>]

Hi Guy,
This is one thing I am confused about.

I am right now setting the sigprocmask
in the callback function :
pkt_callback(...){
 if (sigprocmask(SIG_BLOCK, &block_set, NULL) < 0) {
    perror("sigprocmask");
    exit(1);
  }

....code ...
if (sigprocmask(SIG_UNBLOCK, &block_set, NULL) < 0) {
    perror("sigprocmask");
    exit(1);
  }
}

When I turned down all the alarms, the CPU % usage came down,
as you were also asking to try out.

I think there is lot of overhead in setting up the signal masks etc.

Can i instead set the masks in the main() function before and after calling,
pcap_loop(), which will avoid this overhead ?

I am not sure, I think this will set the masks for the code that pcap runs,
right ?
and block all the signals, which pcap might be using for any purpose, if
any.

Am I right to wrap the pcap_loop() inside the sigprocmask() block, instead
of using
it in callback function (which I am doing now ) ?
<pseudo code>
sigprocmask(block) ..
pcap_loop()
sigprocmask(unblock) ..
</pseudo code>

How will the signals work then ?
-
Abhinav



On Thu, Apr 18, 2013 at 9:06 AM, abhinav narain
<abhinavnarain10 () gmail com>wrote:

> On Thu, Apr 18, 2013 at 8:37 AM, abhinav narain <abhinavnarain10 () gmail com
> > wrote:
>
> > hi Guy,
> >
> > What happens if you eliminate that (and any code paths that eliminating
> > > that breaks)?
> The biggest issue for me to understand is, why is the CPU usage going up
> when
> two instances of the tool run simultaneously. It doesn't have high usage
> for single instance.
> Please let me know, if you have any suggestions where I can make
> my headway to investigate.
> -
> Abhinav
_______________________________________________
tcpdump-workers mailing list
tcpdump-workers () lists tcpdump org
https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers