Messages in this thread | | | Date | Sat, 7 Jul 2007 13:55:03 -0400 | From | "Frank Ch. Eigler" <> | Subject | Re: [patch 10/10] Scheduler profiling - Use immediate values |
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Hi, Adrian -
On Sat, Jul 07, 2007 at 07:01:57PM +0200, Adrian Bunk wrote: > [...] > > Things are not so simple. One might not know that one has a > > performance problem until one tries some analysis tools. Rebooting > > into different kernels just to investigate does not work generally [...] > > I'm not getting this: > > You'll only start looking into an analysis tool if you have a > performance problem, IOW if you are not satisfied with the > performance.
There may be people whose jobs entail continually suspecting performance problems. Or one may run instrumentation code on a long-term basis specifically to locate performance spikes.
> And the debug code will not have been tested on this machine no matter > whether it's enabled through a compile option or at runtime.
There is a big difference in favour of the former. The additional instrumentation code may be small enough to inspect carefully. The rest of the kernel would be unaffected.
> [...] If you might be able to get a big part of tracing and other > debug code enabled with a performance penalty of a few percent of > _kernel_ performance, then you might get much debugging aid without > any effective impact on application performance.
Agreed.
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