Use variables and performance?

AgentUSA · n00b Joined: 15 Jul 2002 Posts: 47

I looked at the Gentoo Guide to USE flags and I was wondering if selecting too many variables would impact performance. I selected a lot of the variables in the guide but I not sure what flags like jpeg, gif or gb actually do. Thanks!

rizzo · Posted: Mon Jul 15, 2002 7:11 pm Post subject:

No they don't affect performance. They affect how programs are compiled when you want to compile them. Having jpeg or gif USE flags will compile jpeg or gif support into programs that check for that flag. Like having the "mysql" flag will tell the qt ebuild to compile in mysql support. qt shouldn't behave better or worse based on it, aside from not supporting mysql if you don't include it.

I definitely recommend going over all the available USE flags, determining what you will or won't need for your system and set them accordingly. Then your machine will pretty much be custom-tailored to your needs.

BonezTheGoon · Posted: Mon Jul 15, 2002 7:14 pm Post subject:

Basically the USE settings are an advanced method of giving your (I say YOUR apps because you are compiling them with your USE settings specific to your machine) apps and binaries options. Each app you compile can refer to your USE settings to see what you wish to support. So IF the app has specific support for JPEG file format that is not enabled by default you over-rode that setting and now your app fully supports JPEG. To answer your question in two different ways (different angles) -- first "no" then "it depends."

No, I have not noticed any performance hit in compiling with TONS of USE settings. Mind you this is only for compiling.

It depends. If you have XMMS (just as some dumb example and this may be a stretch given I don't know if XMMS even exhibits this behavior, but stick with me here this truly is a coherent thought) and you compile in support for KDE and Gnome the executable and supporting libraries will be bigger. Given the executable and the libraries take up more space they will eat more disk resources and memory resources.

So my general strategy is to leave out as much as I am comfortable with, however leave in anything I like the sound of. Any formats I explicitly include (thats just me personally though). Some features I explicitly EXCLUDE, like I have selected to go with ONE Desktop Manager to reduce the size of everything that might have specialized functionality for each. So I hope that I have brought at least SOME light to your question.

Please if I have gone way out in left field just post again and I will try to better answer your question (if I can, I don't know everything--thank goodness.)

Regards,
BonezTheGoon
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BonezTheGoon · Posted: Mon Jul 15, 2002 7:15 pm Post subject:

AgentUSA · n00b Joined: 15 Jul 2002 Posts: 47

Thanks for the replies! I'll go over the variables again and see what I need.

rac · Posted: Tue Nov 19, 2002 6:24 am Post subject:

As I move this out of Newbies, I would like to note that there are a few USE flags that try to affect performance: mmx and 3dnow, at least. With the current state of GCC 3.2, they are not actually likely to have any real effect, however.
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