# Zen -O3

## dE_logics

Has anyone tried this?... I did. I used zen kernel, configured it to be minimal and compiled with -O3 (custom CFLAGS), and it goes pretty fast! With -O2, there was a difference but not that much, turning to O3 just made one helluva difference when I thought it'll break something. That BFS scheduler was of no good... it seemed to me there's no difference between CFQ and BFS, and actually it made things a bit slower, adding more major issues as overhead.

One more difference is I compiled the FSs (except the fs on which my root recedes) as modules.

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## Veldrin

Thanks for sharing - I may have a look at this myself. 

Modules should only make a difference until they are loaded - afterward they should behave as a built in driver...

One word of caution - I read (some years back) that the kernel might not like being compiled as -O3. IIRC there was a case, where an issue only appeared when the kernel was compiled with -O3, but not with -O2. I am not sure if this still applies, but if you ever run into trouble, try -O2 first.

just my .02$

V

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## xaviermiller

Hello,

I had too much unstabilities in 32 bits (i686) with -O3, especially zlib that segfaults...

So, I wouldn't recommand to use -O3 for the kernel.

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## dE_logics

Actually the O3 slowed things down... not the responsiveness but the raw processing power... it was taking twice the compression time, but no stability issues.

However the zen kernel is pretty responsive (and that's about it), I doubt if it has it's overheads.

If I randomly start the default Gentoo kernel or the zen kernel, I can differentiate between the 2 just by responsiveness... even the keyboard feels a bit more responsive.

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## Anon-E-moose

 *dE_logics wrote:*   

>  it seemed to me there's no difference between CFQ and BFS, and actually it made things a bit slower, adding more major issues as overhead.

 

I assume you meant BFQ, not BFS.

There is a difference if you set the RR_INTERVAL, within ZEN_CUSTOM settings. 

The default is six, but I've found with it set to 1, I get really good overall desktop response.

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## dE_logics

Humm... will try it out soon.

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## dE_logics

Nope, CFQ still feels faster.

Actually, the state I'm at, the system cant get more responsive. Now it's limited to the hardware and the ATI driver.

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## Anon-E-moose

Actually I was a touch mixed up myself on what I said.   :Laughing: 

BFQ vs CFQ, I use CFQ (IO sched)

BFS vs CFS, I use BFS (task scheduler)

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## dE_logics

I use deadline in I/O.

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