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    SubjectRe: [PATCH v6] Unified trace buffer
    Steven Rostedt wrote:
    > On Fri, 26 Sep 2008, Mike Travis wrote:
    >
    >> Peter Zijlstra wrote:
    >>> On Fri, 2008-09-26 at 14:05 -0400, Steven Rostedt wrote:
    >>>> +struct ring_buffer {
    >>>> + unsigned long size;
    >>>> + unsigned pages;
    >>>> + unsigned flags;
    >>>> + int cpus;
    >>>> + atomic_t record_disabled;
    >>>> +
    >>>> + struct mutex mutex;
    >>>> +
    >>>> + /* FIXME: this should be online CPUS */
    >>>> + struct ring_buffer_per_cpu *buffers[NR_CPUS];
    >>> actually nr_possible makes sense, and you might consider always
    >>> allocating buffers (and keeping them for offlined cpus) to avoid massive
    >>> allocations/frees cpu-hotplug events.
    >>>
    >>> Mike Travis has been going over the kernel removing constructs like
    >>> this, and replacing them with dynamically allocated arrays of
    >>> nr_possible.
    >>>
    >>>> +};
    >> The other thing to consider is using a percpu variable.
    >
    > This structure is allocated on request.
    >
    > -- Steve


    Ahh, then it would need the yet to be added cpu_alloc() from Christoph.

    Your best bet then is to allocate based on nr_cpu_ids.

    Cheers,
    Mike


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