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SubjectRe: [PATCH v12 2/3]: perf record: enable asynchronous trace writing
On Tue, Oct 09, 2018 at 11:58:53AM +0300, Alexey Budankov wrote:
>
> Trace file offset is read once before mmaps iterating loop and written
> back after all performance data enqueued for aio writing. Trace file offset
> is incremented linearly after every successful aio write operation.
>
> record__aio_sync() blocks till completion of started AIO operation
> and then proceeds.
>
> record__mmap_read_sync() implements a barrier for all incomplete
> aio write requests.
>
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
> Changes in v12:
> - implemented record__aio_get/set_pos(), record__aio_enabled()
> - implemented simple --aio option
> Changes in v11:
> - replacing the both lseek() syscalls in every loop iteration by the only
> two syscalls just before and after the loop at record__mmap_read_evlist()
> and advancing *in-flight* off file pos value at perf_mmap__aio_push()
> Changes in v10:
> - avoided lseek() setting file pos back in case of record__aio_write() failure
> - compacted code selecting between serial and AIO streaming
> - optimized call places of record__mmap_read_sync()
> Changes in v9:
> - enable AIO streaming only when --aio-cblocks option is specified explicitly
> Changes in v8:
> - split AIO completion check into separate record__aio_complete()
> Changes in v6:
> - handled errno == EAGAIN case from aio_write();
> Changes in v5:
> - data loss metrics decreased from 25% to 2x in trialed configuration;
> - avoided nanosleep() prior calling aio_suspend();
> - switched to per cpu multi record__aio_sync() aio
> - record_mmap_read_sync() now does global barrier just before
> switching trace file or collection stop;
> - resolved livelock on perf record -e intel_pt// -- dd if=/dev/zero of=/dev/null count=100000
> Changes in v4:
> - converted void *bf to struct perf_mmap *md in signatures
> - written comment in perf_mmap__push() just before perf_mmap__get();
> - written comment in record__mmap_read_sync() on possible restarting
> of aio_write() operation and releasing perf_mmap object after all;
> - added perf_mmap__put() for the cases of failed aio_write();
> Changes in v3:
> - written comments about nanosleep(0.5ms) call prior aio_suspend()
> to cope with intrusiveness of its implementation in glibc;
> - written comments about rationale behind coping profiling data
> into mmap->data buffer;
> ---
> tools/perf/Documentation/perf-record.txt | 5 +
> tools/perf/builtin-record.c | 220 ++++++++++++++++++++++++++++++-
> tools/perf/perf.h | 1 +
> tools/perf/util/evlist.c | 6 +-
> tools/perf/util/evlist.h | 2 +-
> tools/perf/util/mmap.c | 86 +++++++++++-
> tools/perf/util/mmap.h | 5 +
> 7 files changed, 316 insertions(+), 9 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 246dee081efd..5cedb3e75434 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -435,6 +435,11 @@ Specify vmlinux path which has debuginfo.
> --buildid-all::
> Record build-id of all DSOs regardless whether it's actually hit or not.
>
> +--aio::
> +Enable asynchronous (Posix AIO) trace writing mode.

nit, there's an extra whitespace at the end of above line,
making the 'git am' to not apply your patch

thanks,
jirka

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