Tz

[connortechnology]

Setting the TZ ENV variable prevents every gettimeofday call from reading /etc/timezone which actually has a noticeable performance hit.

[liucougar]

according to: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html

the default value for TZ would be ‘TZ=:/etc/localtime’.

may I know how do you test whether this has a performance hit or not?

[connortechnology]

The problem is.. on my ubuntu and debian based servers, TZ is not set in the ENV.

How I tested was watching cpu consumption on a raspberry pi. I noticed this while stracing zmc, and then setting TZ and watching cpu load. On a low end device like a raspberry pi it is noticeable.

[liucougar]

it seems raspherry pi uses eglibc (not normal glibc), so it may have a different TZ default?

[connortechnology]

This behaviour was seen on ubuntu as well.

If you want to see the behaviour, run strace zmc -m 1 (or whatever monitor id). seems to be worse on a http stream than an rtsp.

Now set TZ and notice that it no longer is hitting /etc/localtime

TZ=:/etc/localtime strace zmc -m 1

[liucougar]

just tried strace on ubuntu 15.04, against a RTSP camera, i am not seeing any call to gettimeofday in my strace log (I don't have http cameras to test against)

[knight-of-ni]

I'm going to merge this as the discussion does not hint at any undesirable side effects.
Let's get this into master so others can test.