From: Riccardo Mancini <email@example.com> To: Arnaldo Carvalho de Melo <firstname.lastname@example.org> Cc: Ian Rogers <email@example.com>, Namhyung Kim <firstname.lastname@example.org>, Peter Zijlstra <email@example.com>, Ingo Molnar <firstname.lastname@example.org>, Mark Rutland <email@example.com>, Jiri Olsa <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, Alexey Bayduraev <email@example.com>, Riccardo Mancini <firstname.lastname@example.org> Subject: [RFC PATCH v2 00/10] perf: add workqueue library and use it in synthetic-events Date: Fri, 30 Jul 2021 17:34:07 +0200 [thread overview] Message-ID: <email@example.com> (raw) Changes in v2: - rename threadpool_struct and its functions to adhere to naming style - use ERR_PTR instead of returning NULL - add *__strerror functions, removing pr_err from library code - wait for threads after creation of all threads, instead of waiting after each creation - use intention-revealing macros in test code instead of 0 and -1 - use readn/writen functions v1: https://firstname.lastname@example.org/ This patchset introduces a new utility library inside perf/util, which provides a work queue abstraction, which loosely follows the Kernel workqueue API. The workqueue abstraction is made up by two components: - threadpool: which takes care of managing a pool of threads. It is inspired by the prototype for threaded trace in perf-record from Alexey: https://email@example.com/ - workqueue: manages a shared queue and provides the workers implementation. On top of the workqueue, a simple parallel-for utility is implemented which is then showcased in synthetic-events.c, replacing the previous manual pthread-created threads. Through some experiments with perf bench, I can see how the new workqueue has a slightly higher overhead compared to manual creation of threads, but is able to more effectively partition work among threads, yielding better results overall. Furthermore, the overhead could be reduced by changing the `work_size` (currently 1), aka the number of dirents that are processed by a thread before grabbing a lock to get the new work item. I experimented with different sizes but, while bigger sizes reduce overhead as expected, they do not scale as well to more threads. I believe the next steps are, in order: - add support to specifying affinities to threads. - add worker queues with round robin assignment (replacing the current shared queue). - optionally add work stealing among the worker queues. I'd keep it a future work for the moment since we do not have a specific use case for it at the moment (the synthetic threads would not benefit too much from it imo). - add support to executing jobs on a specific worker (which will have its own affinity). This is useful for Alexey's usecase and for the following evlist open usecase. - make workqueue directly manage the threadpool (as Arnaldo already suggested). We could also make the workqueue global but that requires an autogrow feature so that threads are created on demand and not all at the beginning. I'd keep it a future work. - apply workqueue to the evlist open (the idea is to pin each thread to a GPU and submit a work_struct for each evsel/cpu to the matching cpu). Any comment or idea is highly appreciated. Thanks, Riccardo Riccardo Mancini (10): perf workqueue: threadpool creation and destruction perf tests: add test for workqueue perf workqueue: add threadpool start and stop functions perf workqueue: add threadpool execute and wait functions tools: add sparse context/locking annotations in compiler-types.h perf workqueue: introduce workqueue struct perf workqueue: implement worker thread and management perf workqueue: add queue_work and flush_workqueue functions perf workqueue: add utility to execute a for loop in parallel perf synthetic-events: use workqueue parallel_for tools/include/linux/compiler_types.h | 18 + tools/perf/tests/Build | 1 + tools/perf/tests/builtin-test.c | 9 + tools/perf/tests/tests.h | 3 + tools/perf/tests/workqueue.c | 450 +++++++++++++++ tools/perf/util/Build | 1 + tools/perf/util/synthetic-events.c | 155 ++--- tools/perf/util/workqueue/Build | 2 + tools/perf/util/workqueue/threadpool.c | 674 ++++++++++++++++++++++ tools/perf/util/workqueue/threadpool.h | 40 ++ tools/perf/util/workqueue/workqueue.c | 750 +++++++++++++++++++++++++ tools/perf/util/workqueue/workqueue.h | 51 ++ 12 files changed, 2080 insertions(+), 74 deletions(-) create mode 100644 tools/perf/tests/workqueue.c create mode 100644 tools/perf/util/workqueue/Build create mode 100644 tools/perf/util/workqueue/threadpool.c create mode 100644 tools/perf/util/workqueue/threadpool.h create mode 100644 tools/perf/util/workqueue/workqueue.c create mode 100644 tools/perf/util/workqueue/workqueue.h -- 2.31.1
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