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From: Tom de Vries <vries@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] [gdbsupport] Add parallel_for_each_debug Date: Mon, 18 Jul 2022 03:34:04 +0000 (GMT) [thread overview] Message-ID: <20220718033404.C87F53858CDA@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=53944a3bf51cdff9ad30a0c3740b8124213fdab9 commit 53944a3bf51cdff9ad30a0c3740b8124213fdab9 Author: Tom de Vries <tdevries@suse.de> Date: Mon Jul 18 05:34:01 2022 +0200 [gdbsupport] Add parallel_for_each_debug Add a parallel_for_each_debug variable, set to false by default. With an a.out compiled from hello world, we get with parallel_for_each_debug == true: ... $ gdb -q -batch a.out -ex start ... Parallel for: n_elements: 7271 Parallel for: minimum elements per thread: 10 Parallel for: elts_per_thread: 1817 Parallel for: elements on worker thread 0 : 1817 Parallel for: elements on worker thread 1 : 1817 Parallel for: elements on worker thread 2 : 1817 Parallel for: elements on worker thread 3 : 0 Parallel for: elements on main thread : 1820 Temporary breakpoint 1, main () at /home/vries/hello.c:6 6 printf ("hello\n"); ... Tested on x86_64-linux. Diff: --- gdbsupport/parallel-for.h | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/gdbsupport/parallel-for.h b/gdbsupport/parallel-for.h index a614fc35766..cfe8a6e4f09 100644 --- a/gdbsupport/parallel-for.h +++ b/gdbsupport/parallel-for.h @@ -139,7 +139,12 @@ parallel_for_each (unsigned n, RandomIt first, RandomIt last, using result_type = typename std::result_of<RangeFunction (RandomIt, RandomIt)>::type; - size_t n_threads = thread_pool::g_thread_pool->thread_count (); + /* If enabled, print debug info about how the work is distributed across + the threads. */ + const int parallel_for_each_debug = false; + + size_t n_worker_threads = thread_pool::g_thread_pool->thread_count (); + size_t n_threads = n_worker_threads; size_t n_elements = last - first; size_t elts_per_thread = 0; if (n_threads > 1) @@ -155,9 +160,19 @@ parallel_for_each (unsigned n, RandomIt first, RandomIt last, size_t count = n_threads == 0 ? 0 : n_threads - 1; gdb::detail::par_for_accumulator<result_type> results (count); + if (parallel_for_each_debug) + { + debug_printf (_("Parallel for: n_elements: %zu\n"), n_elements); + debug_printf (_("Parallel for: minimum elements per thread: %u\n"), n); + debug_printf (_("Parallel for: elts_per_thread: %zu\n"), elts_per_thread); + } + for (int i = 0; i < count; ++i) { RandomIt end = first + elts_per_thread; + if (parallel_for_each_debug) + debug_printf (_("Parallel for: elements on worker thread %i\t: %zu\n"), + i, (size_t)(end - first)); results.post (i, [=] () { return callback (first, end); @@ -165,7 +180,14 @@ parallel_for_each (unsigned n, RandomIt first, RandomIt last, first = end; } + for (int i = count; i < n_worker_threads; ++i) + if (parallel_for_each_debug) + debug_printf (_("Parallel for: elements on worker thread %i\t: 0\n"), i); + /* Process all the remaining elements in the main thread. */ + if (parallel_for_each_debug) + debug_printf (_("Parallel for: elements on main thread\t\t: %zu\n"), + (size_t)(last - first)); return results.finish ([=] () { return callback (first, last);
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