Messages in this thread | | | From | Riccardo Mancini <> | Subject | [RFC PATCH v3 00/15] perf: add workqueue library and use it in synthetic-events | Date | Fri, 20 Aug 2021 12:53:46 +0200 |
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Changes in v3: - improved separation of threadpool and threadpool_entry method - replaced shared workqueue with per-thread workqueue. This should improve the performance on big machines (Jiri noticed in his experiments a significant performance degradation after 15 threads with the shared queue). - improved error reporting in both threadpool and workqueue - added lazy spinup of threads in workqueue [9/15] - added global workqueue [10/15] - setup global workqueue in perf record, top and synthesize bench [12-14/15] and used in in synthetic events
v2: https://lore.kernel.org/lkml/cover.1627643744.git.rickyman7@gmail.com/ https://lore.kernel.org/lkml/4f0cd6c8e77c0b4f4d4b8d553a7032757b976e61.1627657061.git.rickyman7@gmail.com/ (something went wrong when sending it and the cover letter has a wrong Message-Id)
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://lkml.kernel.org/lkml/cover.1626177381.git.rickyman7@gmail.com/
This patchset introduces a new utility library inside perf/util, which provides a work queue abstraction, which 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://lore.kernel.org/lkml/cover.1625227739.git.alexey.v.bayduraev@linux.intel.com/ - workqueue: manages the workers in the threadpool and assigns the work items to the thread-local queues.
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 (see the last patch for benchmark detaisl on my machine). Since I'm not able to test it on bigger machine, it would be helpful if someone could also test it and report back his results (thanks to Jiri and Arnaldo who have already helped me by doing some tests).
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.
Soon I will also send another patchset applying the workqueue to evlist operations (open, enable, disable, close).
Thanks, Riccardo
Riccardo Mancini (15): 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: spinup threads when needed perf workqueue: create global workqueue perf workqueue: add utility to execute a for loop in parallel perf record: setup global workqueue perf top: setup global workqueue perf test/synthesis: setup global workqueue perf synthetic-events: use workqueue parallel_for
tools/include/linux/compiler_types.h | 18 + tools/perf/bench/synthesize.c | 28 +- tools/perf/builtin-kvm.c | 2 +- tools/perf/builtin-record.c | 18 +- tools/perf/builtin-top.c | 19 +- tools/perf/builtin-trace.c | 3 +- tools/perf/tests/Build | 1 + tools/perf/tests/builtin-test.c | 9 + tools/perf/tests/mmap-thread-lookup.c | 2 +- tools/perf/tests/tests.h | 3 + tools/perf/tests/workqueue.c | 453 +++++++++++++ tools/perf/util/Build | 1 + tools/perf/util/synthetic-events.c | 135 ++-- tools/perf/util/synthetic-events.h | 8 +- tools/perf/util/workqueue/Build | 2 + tools/perf/util/workqueue/threadpool.c | 619 +++++++++++++++++ tools/perf/util/workqueue/threadpool.h | 41 ++ tools/perf/util/workqueue/workqueue.c | 901 +++++++++++++++++++++++++ tools/perf/util/workqueue/workqueue.h | 104 +++ 19 files changed, 2253 insertions(+), 114 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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