Re: Unified tracing buffer

[KOSAKI Motohiro]

> By the way, systemtap uses two modes;
> 
> - single-channel mode
>  In this mode, all cpus share one buffer channel to write and read.
>  each writer locks spinlock and write a probe-local data to buffer.
> 
> - per-cpu buffer mode
>  In this mode, we use an atomic sequential number for ordering data. If
>  user doesn't need it(because they have their own timestamps), they can
>  choose not to use that seq-number.

I can't imazine a merit of the single-channel mode.
Could you please explain it?

Because some architecture don't have fine grained timestamp?
if so, could you explain which architecture don't have it?



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