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Re: Questions about STP_TIMING

Frank Ch. Eigler wrote:

Hi -

On Thu, Jan 25, 2007 at 03:04:37PM -0800, Stone, Joshua I wrote:

I have a couple of questions about STP_TIMING. First, why are the cycle
counts truncated to 32-bits? [...]

This was my doing, in response to learning someplace that some popular processors' cycle counters are relatively short before wrapping - longer than 32 bits but shorter than 64. Since individual probe handlers tend to run for much shorter intervals than billions of cycles, 32 seemed like a good general compromise.

When/if we start supporting non-atomic probe handlers, then this part
will need to be revisited, for example since the "less than billions
of cycles" assumption will become invalid.

I interpret your atomic probe handlers mean the handler that runs without sleeping/pre-emption to completion. User space probes handlers can sleep (Jim correct me if i am wrong). This may be one of the things we have to revisit when we start supporting uprobes.

Vara Prasad

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