From: Tom Tromey <tom@tromey.com>
To: gdb-patches@sourceware.org
Cc: Tom Tromey <tom@tromey.com>
Subject: [PATCH v2 10/32] Add batching parameter to parallel_for_each
Date: Thu, 4 Nov 2021 12:08:45 -0600 [thread overview]
Message-ID: <20211104180907.2360627-11-tom@tromey.com> (raw)
In-Reply-To: <20211104180907.2360627-1-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:[~2021-11-04 18:09 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-04 18:08 [PATCH v2 00/32] Rewrite the DWARF "partial" reader Tom Tromey
2021-11-04 18:08 ` [PATCH v2 01/32] Introduce make_unique_xstrndup Tom Tromey
2021-11-05 19:20 ` Simon Marchi
2021-11-05 20:08 ` Tom Tromey
2021-11-04 18:08 ` [PATCH v2 02/32] Split create_addrmap_from_aranges Tom Tromey
2021-11-04 18:08 ` [PATCH v2 03/32] Add dwarf2_per_cu_data::addresses_seen Tom Tromey
2021-11-04 18:08 ` [PATCH v2 04/32] Refactor dwarf2_get_pc_bounds Tom Tromey
2021-11-05 19:51 ` Simon Marchi
2021-11-24 15:53 ` Tom Tromey
2021-11-04 18:08 ` [PATCH v2 05/32] Allow ada_decode not to decode operators Tom Tromey
2021-11-04 18:08 ` [PATCH v2 06/32] Let skip_one_die not skip children Tom Tromey
2021-11-04 18:08 ` [PATCH v2 07/32] Add name splitting Tom Tromey
2021-11-04 18:08 ` [PATCH v2 08/32] Add new overload of dwarf5_djb_hash Tom Tromey
2021-11-05 20:01 ` Simon Marchi
2021-11-07 17:02 ` Tom Tromey
2021-11-04 18:08 ` [PATCH v2 09/32] Refactor build_type_psymtabs_reader Tom Tromey
2021-11-04 18:08 ` Tom Tromey [this message]
2021-11-04 18:08 ` [PATCH v2 11/32] Return vector of results from parallel_for_each Tom Tromey
2021-11-17 20:37 ` Lancelot SIX
2021-11-18 14:41 ` Tom Tromey
2021-11-04 18:08 ` [PATCH v2 12/32] Specialize std::hash for gdb_exception Tom Tromey
2021-11-04 18:08 ` [PATCH v2 13/32] Introduce DWARF abbrev cache Tom Tromey
2021-11-04 18:08 ` [PATCH v2 14/32] Statically examine abbrev properties Tom Tromey
2021-11-04 18:08 ` [PATCH v2 15/32] Update skip_one_die for new " Tom Tromey
2021-11-04 18:08 ` [PATCH v2 16/32] Introduce the new DWARF index class Tom Tromey
2021-11-04 18:08 ` [PATCH v2 17/32] The new DWARF indexer Tom Tromey
2021-11-04 18:08 ` [PATCH v2 18/32] Implement quick_symbol_functions for cooked DWARF index Tom Tromey
2021-11-04 18:08 ` [PATCH v2 19/32] Wire in the new DWARF indexer Tom Tromey
2021-11-04 18:08 ` [PATCH v2 20/32] Introduce thread-safe handling for complaints Tom Tromey
2021-11-04 18:08 ` [PATCH v2 21/32] Pre-read DWARF section data Tom Tromey
2021-11-04 18:08 ` [PATCH v2 22/32] Parallelize DWARF indexing Tom Tromey
2021-11-04 18:08 ` [PATCH v2 23/32] "Finalize" the DWARF index in the background Tom Tromey
2021-11-04 18:08 ` [PATCH v2 24/32] Rename write_psymtabs_to_index Tom Tromey
2021-11-04 18:09 ` [PATCH v2 25/32] Change the key type in psym_index_map Tom Tromey
2021-11-04 18:09 ` [PATCH v2 26/32] Change parameters to write_address_map Tom Tromey
2021-11-04 18:09 ` [PATCH v2 27/32] Genericize addrmap handling in the DWARF index writer Tom Tromey
2021-11-04 18:09 ` [PATCH v2 28/32] Adapt .gdb_index writer to new DWARF scanner Tom Tromey
2021-11-04 18:09 ` [PATCH v2 29/32] Adapt .debug_names " Tom Tromey
2021-11-04 18:09 ` [PATCH v2 30/32] Enable the new DWARF indexer Tom Tromey
2021-11-04 18:09 ` [PATCH v2 31/32] Delete DWARF psymtab code Tom Tromey
2021-11-04 18:09 ` [PATCH v2 32/32] Remove dwarf2_per_cu_data::v Tom Tromey
2021-11-06 12:25 ` [PATCH v2 00/32] Rewrite the DWARF "partial" reader Tom de Vries
2021-11-11 12:23 ` Tom de Vries
2021-11-16 23:56 ` Tom Tromey
2021-11-17 9:22 ` Tom de Vries
2021-11-18 14:43 ` Tom Tromey
2021-11-22 19:59 ` Tom Tromey
2021-11-22 20:52 ` Tom de Vries
2021-11-22 22:11 ` Tom Tromey
2021-11-23 7:56 ` Tom de Vries
2021-11-23 17:00 ` Tom Tromey
2021-11-08 17:41 ` Simon Marchi
2021-11-10 19:56 ` Tom Tromey
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