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SubjectRe: [PATCH 0/6] perf core: Read from overwrite ring buffer
Hi,

On Tue, Jan 19, 2016 at 11:16:44AM +0000, Wang Nan wrote:
> This patchset introduces two methods to support reading from overwrite.
>
> 1) Tailsize: write the size of an event at the end of it
> 2) Backward writing: write the ring buffer from the end of it to the
> beginning.

So both of two methods should be used together?

Thanks,
Namhyung


>
> Patch 1/6 introduces a new ioctl operation to pause and resume ring
> buffer since reading from a overwrite ring buffer is not reliable.
>
> To reduce overhead as much as possible, force setting overflow_handler
> and create specific function for backward writing and onward writing.
>
> Cc: He Kuang <hekuang@huawei.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
>
> Wang Nan (6):
> perf core: Introduce new ioctl options to pause and resume ring buffer
> perf core: Set event's default overflow_handler
> perf core: Prepare writing into ring buffer from end
> perf core: Add backwork attribute to perf event
> perf core: Reduce perf event output overhead by setting overwrite
> handler
> perf/core: Put size of a sample at the end of it by
> PERF_SAMPLE_TAILSIZE
>
> include/linux/perf_event.h | 39 +++++++---
> include/uapi/linux/perf_event.h | 7 +-
> kernel/events/core.c | 155 +++++++++++++++++++++++++++++++---------
> kernel/events/internal.h | 11 +++
> kernel/events/ring_buffer.c | 65 ++++++++++++++---
> 5 files changed, 223 insertions(+), 54 deletions(-)
>
> --
> 1.8.3.4
>

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