Screenshot processing

[florczakraf]

Hey. Recently I tried to make use of the sv_screenshotArrivedCmd. I wrote a python script to extract meta-data from the screenshot and draw it on the picture itself. Script does it's job, however I experience the lag on the server each time a new screenshot has arrived. It's local lag -- not shared between other game servers I run on the same machine (i.e. only server that's processing screenshots at the time is affected). The lag is noticeable even without lagometer on -- server freezes for a moment so players experience teleporting.

Here's short video to visualize the issue: https://www.youtube.com/watch?v=FgIVT6_pOhc (you can see spikes on the lagometer at the moment of console outputting Screenshot for client ... saved to screenshots/...).

Here are my questions:

1. Have you actually tested this feature? 😏
2. Is it normal that there is such a huge overhead for creating new process with execv? (I couldn't find reliable source on the net.)
3. Am I doing something wrong?

More info:
I can provide my script if needed, although the issue exists even with empty python script:

#!/usr/bin/python3
if __name__ == '__main__':
   pass

or this c program 😏:

int main()
{
    return 0;
}

[IceNinjaman]

Hi there,
I have to admit to not having tested this feature. Isn't it fork() + execv() ?
If your cod4server process start to lag it is probably caused by a function call which does block for some time. Maybe fork() is doing this? Although fork() is part of many daemons you can find on *nix systems. There a little bit lag is maybe not the issue? I don't really know how to do it better.
Creating a new thread to fork() then?

[T-Maxxx]

fork() and execv() are very expensive operations. But yeah, forking in other thread should do the trick.
https://github.com/D4edalus/CoD4x_Server/blob/master/src/unix/sys_unix.c#L108

[D4edalus]

imho it would be best to just have a plugin callback

2016-07-17 0:30 GMT+02:00 Max notifications@github.com:

fork() and execv() are very expensive operations. But yeah, forking in
other thread should do the trick.

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[IceNinjaman]

In current version it is replaced by creating a new thread and invoking system(). Would be nice to know if it works and if it works better. You need however this library for screenshots you can find on forum.

[florczakraf]

Alright, I will try to give it a go tonight.

[florczakraf]

Did not help at all (tested with empty c program as screenshot processor). I noticed that you now wait till player sees someone to take a screenshot 👍

[IceNinjaman]

You are saying it still doing lag?

[florczakraf]

That's exactly what I'm saying.

On 11 August 2016 at 02:33, IceNinjaman notifications@github.com wrote:

You are saying it still doing lag?

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[IceNinjaman]

Okay well then I have no idea how to improve it. Is your host weak in general?

[florczakraf]

Don't think so.
CPU: Intel Xeon E3 1245v2 4 cores/ 8 threads 3.4 GHz+
RAM: 32GB DDR3
DISK: 2 x 2 TB SATA (soft raid)
We host some cod4 server, ts, some webtools, and a minecraft server there. Low resource usage.

[IceNinjaman]

Okay I still can't do anything if launching a new process does load the whole system so much.

[florczakraf]

It doesn't load whole system, that's the point. It only makes the server that's currently receiving screenshots lag. Anyway, thanks for trying.

[D4edalus]

D4edalus@8a0a312

added a plugin callback to enable a more leightweight screenshot processing and avoid manual parsing.