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    Subject[PATCH] perf record: Add snapshot mode support for perf's regular events
    Date
    This idea is issued and motivated from:
    https://lwn.net/Articles/650499/

    After the first RFC is sent:
    http://lkml.iu.edu/hypermail/linux/kernel/1509.2/04347.html

    Both David Ahern and Borislav Petkov have replied to that RFC:
    http://lkml.iu.edu/hypermail/linux/kernel/1509.2/04350.html
    http://lkml.iu.edu/hypermail/linux/kernel/1509.2/03914.html

    Thanks to David's and Borislav's advice.

    However, David's perf-based scheduling daemon just makes some count when
    the signal triggers perf sched, with no sample recording and has nothing
    to do with perf.data. As for Borislav's persistent events, when perf
    record runs, it just makes fd to attach to the persistent event to read,
    and all the persistent event's tracing info will still dump to perf.data
    during perf's running.

    As a result, neither David's nor Borislav's patches makes the similar
    snapshot mode support as what aux trace does.

    In our patch, we create and maintain a user space ring buffer to store
    perf's tracing info, instead of directly writing to perf.data file as
    before. In snapshot mode, only a SIGUSR2 signal can trigger perf to dump
    the tracing info currently stored in the user space ring buffer to
    perf.data file.

    Yunlong Song (1):
    perf record: Add snapshot mode support for perf's regular events

    tools/perf/builtin-record.c | 181 +++++++++++++++++++++++++++++++++++++++++---
    1 file changed, 170 insertions(+), 11 deletions(-)

    --
    1.8.5.2



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