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    SubjectRe: [PATCH 02/17] perf tools: Add evlist channel helpers
    Em Wed, May 18, 2016 at 11:27:43AM +0800, Wangnan (F) escreveu:
    > On 2016/5/13 21:05, Arnaldo Carvalho de Melo wrote:
    > >Em Fri, May 13, 2016 at 07:55:59AM +0000, Wang Nan escreveu:
    > >> Channels hold different groups of evsels which configured
    > >> differently. It will be used for overwritable evsels, which allows
    > >> perf

    > >why not use multiple evlists? An "evlist" is a "list of evsels", why do
    > >we need yet another way of grouping evlists?

    > There's an assumption all over perf that there's only one evlist: in
    > 'struct record' there's an 'evlist' pointer, in 'struct session'
    > there's also an 'evlist' pointer.

    Well, at some point there were none, and multiple tools used multiple
    ways to deal with lists of events :-)

    > Trying to change them to an array results in 181 errors, so I think
    > fundamentally moving to multiple evlists is nearly impossible.

    Well, in the next paragraph you give it some hope :-)

    > Now I'm thinking introducing auxiliary evlists to perf record. We
    > still obey one evlist assumption, only creates separated evlists for
    > mmap.

    Ok, that may be the way to go, i.e. linking evlists somehow for some
    specific use cases, i.e. consuming events from multiple evlists,
    probably sorting them via the ordered_events class, etc.

    I have to review this more deeply to try and come with suggestions :-\

    - Arnaldo

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