From: Tom Tromey <tom@tromey.com>
To: gdb-patches@sourceware.org
Cc: Tom Tromey <tom@tromey.com>
Subject: [PATCH v3 10/33] Add batching parameter to parallel_for_each
Date: Sat, 4 Dec 2021 13:38:21 -0700 [thread overview]
Message-ID: <20211204203844.1188999-11-tom@tromey.com> (raw)
In-Reply-To: <20211204203844.1188999-1-tom@tromey.com>
parallel_for_each currently requires each thread to process at least
10 elements. However, when indexing, it's fine for a thread to handle
just a single CU. This patch parameterizes this, and updates the one
user.
---
gdb/minsyms.c | 4 ++--
gdb/unittests/parallel-for-selftests.c | 2 +-
gdbsupport/parallel-for.h | 18 ++++++++++++------
3 files changed, 15 insertions(+), 9 deletions(-)
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 5f4cf54c663..7f2f23dd789 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -1462,8 +1462,8 @@ minimal_symbol_reader::install ()
std::vector<computed_hash_values> hash_values (mcount);
msymbols = m_objfile->per_bfd->msymbols.get ();
- gdb::parallel_for_each
- (&msymbols[0], &msymbols[mcount],
+ /* Arbitrarily require at least 10 elements in a thread. */
+ gdb::parallel_for_each (10, &msymbols[0], &msymbols[mcount],
[&] (minimal_symbol *start, minimal_symbol *end)
{
for (minimal_symbol *msym = start; msym < end; ++msym)
diff --git a/gdb/unittests/parallel-for-selftests.c b/gdb/unittests/parallel-for-selftests.c
index f149e72f0c7..c7a3780c743 100644
--- a/gdb/unittests/parallel-for-selftests.c
+++ b/gdb/unittests/parallel-for-selftests.c
@@ -52,7 +52,7 @@ test (int n_threads)
#define NUMBER 10000
std::atomic<int> counter (0);
- gdb::parallel_for_each (0, NUMBER,
+ gdb::parallel_for_each (1, 0, NUMBER,
[&] (int start, int end)
{
counter += end - start;
diff --git a/gdbsupport/parallel-for.h b/gdbsupport/parallel-for.h
index e4fcb4053b2..54027e69402 100644
--- a/gdbsupport/parallel-for.h
+++ b/gdbsupport/parallel-for.h
@@ -35,11 +35,16 @@ namespace gdb
This approach was chosen over having the callback work on single
items because it makes it simple for the caller to do
- once-per-subrange initialization and destruction. */
+ once-per-subrange initialization and destruction.
+
+ The parameter N says how batching ought to be done -- there will be
+ at least N elements processed per thread. Setting N to 0 is not
+ allowed. */
template<class RandomIt, class RangeFunction>
void
-parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
+parallel_for_each (unsigned n, RandomIt first, RandomIt last,
+ RangeFunction callback)
{
#if CXX_STD_THREAD
/* So we can use a local array below. */
@@ -52,10 +57,11 @@ parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
size_t n_elements = last - first;
if (n_threads > 1)
{
- /* Arbitrarily require that there should be at least 10 elements
- in a thread. */
- if (n_elements / n_threads < 10)
- n_threads = std::max (n_elements / 10, (size_t) 1);
+ /* Require that there should be at least N elements in a
+ thread. */
+ gdb_assert (n > 0);
+ if (n_elements / n_threads < n)
+ n_threads = std::max (n_elements / n, (size_t) 1);
size_t elts_per_thread = n_elements / n_threads;
n_actual_threads = n_threads - 1;
for (int i = 0; i < n_actual_threads; ++i)
--
2.31.1
next prev parent reply other threads:[~2021-12-04 20:39 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-04 20:38 [PATCH v3 00/33] Rewrite the DWARF "partial" reader Tom Tromey
2021-12-04 20:38 ` [PATCH v3 01/33] Split create_addrmap_from_aranges Tom Tromey
2021-12-04 20:38 ` [PATCH v3 02/33] Fix latent bug in read_addrmap_from_aranges Tom Tromey
2021-12-04 20:38 ` [PATCH v3 03/33] Add dwarf2_per_cu_data::addresses_seen Tom Tromey
2021-12-04 20:38 ` [PATCH v3 04/33] Refactor dwarf2_get_pc_bounds Tom Tromey
2021-12-04 20:38 ` [PATCH v3 05/33] Allow ada_decode not to decode operators Tom Tromey
2021-12-04 20:38 ` [PATCH v3 06/33] Let skip_one_die not skip children Tom Tromey
2021-12-04 20:38 ` [PATCH v3 07/33] Add name splitting Tom Tromey
2021-12-04 20:38 ` [PATCH v3 08/33] Add new overload of dwarf5_djb_hash Tom Tromey
2021-12-04 20:38 ` [PATCH v3 09/33] Refactor build_type_psymtabs_reader Tom Tromey
2021-12-04 20:38 ` Tom Tromey [this message]
2021-12-04 20:38 ` [PATCH v3 11/33] Return vector of results from parallel_for_each Tom Tromey
2022-03-29 17:36 ` Pedro Alves
2022-03-29 20:07 ` Tom Tromey
2021-12-04 20:38 ` [PATCH v3 12/33] Specialize std::hash for gdb_exception Tom Tromey
2021-12-04 20:38 ` [PATCH v3 13/33] Add "fullname" handling to file_and_directory Tom Tromey
2021-12-07 17:17 ` Tom Tromey
2021-12-04 20:38 ` [PATCH v3 14/33] Introduce DWARF abbrev cache Tom Tromey
2021-12-04 20:38 ` [PATCH v3 15/33] Statically examine abbrev properties Tom Tromey
2021-12-04 20:38 ` [PATCH v3 16/33] Update skip_one_die for new " Tom Tromey
2021-12-04 20:38 ` [PATCH v3 17/33] Introduce the new DWARF index class Tom Tromey
2021-12-04 20:38 ` [PATCH v3 18/33] The new DWARF indexer Tom Tromey
2022-03-29 18:04 ` Pedro Alves
2022-03-29 20:08 ` Tom Tromey
2021-12-04 20:38 ` [PATCH v3 19/33] Implement quick_symbol_functions for cooked DWARF index Tom Tromey
2021-12-04 20:38 ` [PATCH v3 20/33] Wire in the new DWARF indexer Tom Tromey
2021-12-04 20:38 ` [PATCH v3 21/33] Introduce thread-safe handling for complaints Tom Tromey
2021-12-04 20:38 ` [PATCH v3 22/33] Pre-read DWARF section data Tom Tromey
2021-12-04 20:38 ` [PATCH v3 23/33] Parallelize DWARF indexing Tom Tromey
2022-03-30 10:24 ` Pedro Alves
2022-03-30 20:23 ` Tom Tromey
2022-03-30 21:24 ` Tom Tromey
2021-12-04 20:38 ` [PATCH v3 24/33] "Finalize" the DWARF index in the background Tom Tromey
2021-12-04 20:38 ` [PATCH v3 25/33] Rename write_psymtabs_to_index Tom Tromey
2021-12-04 20:38 ` [PATCH v3 26/33] Change the key type in psym_index_map Tom Tromey
2021-12-04 20:38 ` [PATCH v3 27/33] Change parameters to write_address_map Tom Tromey
2021-12-04 20:38 ` [PATCH v3 28/33] Genericize addrmap handling in the DWARF index writer Tom Tromey
2021-12-04 20:38 ` [PATCH v3 29/33] Adapt .gdb_index writer to new DWARF scanner Tom Tromey
2021-12-04 20:38 ` [PATCH v3 30/33] Adapt .debug_names " Tom Tromey
2021-12-04 20:38 ` [PATCH v3 31/33] Enable the new DWARF indexer Tom Tromey
2021-12-04 20:38 ` [PATCH v3 32/33] Delete DWARF psymtab code Tom Tromey
2021-12-04 20:38 ` [PATCH v3 33/33] Remove dwarf2_per_cu_data::v Tom Tromey
2022-01-05 17:18 ` [PATCH v3 00/33] Rewrite the DWARF "partial" reader Tom Tromey
2022-03-24 16:18 ` Tom Tromey
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