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SubjectRe: [PATCH 4/4] ring-buffer: only allocate buffers for online cpus
> From: Steven Rostedt <>
> Impact: save on memory
> Currently, a ring buffer was allocated for each "possible_cpus". On
> some systems, this is the same as NR_CPUS. Thus, if a system defined
> NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless
> ring buffers taking up space. With a default buffer of 3 megs, this
> could be quite drastic.
> This patch changes the ring buffer code to only allocate ring buffers
> for online CPUs. If a CPU goes off line, we do not free the buffer.
> This is because the user may still have trace data in that buffer
> that they would like to look at.
> Perhaps in the future we could add code to delete a ring buffer if
> the CPU is offline and the ring buffer becomes empty.

I don't like this patch.
your [1/4] and [2/4] already solve Pierre's problem.

using online cpu (not possible cpu) increase performance overhead
and messiness.
but nobody get benefit ;)

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