Re: [RFC] [Patch 0/8] statistics infrastructure

From: Valdis . Kletnieks
Date: Wed May 17 2006 - 14:44:59 EST

On Wed, 17 May 2006 14:28:08 EDT, "Frank Ch. Eigler" said:
> I am not suggesting a single solution for all needs. I wanted to
> focus only one aspect: the marking of those points in the kernel where
> something probeworthy occurs with hooks. The different tools would
> still gather and disseminate their data in their own favorite. The
> main difference from the status quo is agreeing on and reusing a
> common pool of hooks.

The problem is that the "common pool" ends up being a very wide swamp
very fast. The last few times I've needed any instrumentation in the
kernel, I was chasing slab leaks, and didn't need precise timing or
latency measurements. On the other hand, the RT guys probably don't
care all that much about slab events, but need timing and latency.
Then there's other guys that don't care about slab, timing, or latency,
but do care about some other events.

So under your plan, all 3 groups now use a "common pool" that includes
slap, timing, latency, and other stuff - and nobody's using more than
1/3 of it, but paying the performance penalty for the 2/3 unused hooks....

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