From: Tom Tromey <tom@tromey.com>
To: gdb-patches@sourceware.org
Cc: Tom Tromey <tom@tromey.com>
Subject: [PATCH 10/30] Add batching parameter to parallel_for_each
Date: Wed, 25 Aug 2021 20:19:17 -0600 [thread overview]
Message-ID: <20210826021937.1490292-11-tom@tromey.com> (raw)
In-Reply-To: <20210826021937.1490292-1-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 ++--
gdbsupport/parallel-for.h | 18 ++++++++++++------
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 33560e3c41c..1c124848c28 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/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:[~2021-08-26 2:19 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-26 2:19 [PATCH 00/30] Rewrite the DWARF "partial" reader Tom Tromey
2021-08-26 2:19 ` [PATCH 01/30] Introduce make_unique_xstrndup Tom Tromey
2021-08-26 2:19 ` [PATCH 02/30] Split create_addrmap_from_aranges Tom Tromey
2021-08-26 2:19 ` [PATCH 03/30] Add dwarf2_per_cu_data::addresses_seen Tom Tromey
2021-08-26 2:19 ` [PATCH 04/30] Refactor dwarf2_get_pc_bounds Tom Tromey
2021-08-26 2:19 ` [PATCH 05/30] Allow ada_decode not to decode operators Tom Tromey
2021-08-26 2:19 ` [PATCH 06/30] Let skip_one_die not skip children Tom Tromey
2021-08-26 2:19 ` [PATCH 07/30] Add name splitting Tom Tromey
2021-08-26 2:19 ` [PATCH 08/30] Add new overload of dwarf5_djb_hash Tom Tromey
2021-08-26 2:19 ` [PATCH 09/30] Refactor build_type_psymtabs_reader Tom Tromey
2021-08-26 2:19 ` Tom Tromey [this message]
2021-08-26 2:19 ` [PATCH 11/30] Return vector of results from parallel_for_each Tom Tromey
2021-08-27 6:20 ` Tom de Vries
2021-08-28 19:20 ` Tom Tromey
2021-08-26 2:19 ` [PATCH 12/30] Introduce DWARF abbrev cache Tom Tromey
2021-08-26 2:19 ` [PATCH 13/30] Statically examine abbrev properties Tom Tromey
2021-09-06 22:31 ` Lancelot SIX
2021-11-04 18:00 ` Tom Tromey
2021-08-26 2:19 ` [PATCH 14/30] Update skip_one_die for new " Tom Tromey
2021-08-26 2:19 ` [PATCH 15/30] Introduce the new DWARF index class Tom Tromey
2021-09-09 23:32 ` Lancelot SIX
2021-11-04 18:03 ` Tom Tromey
2021-08-26 2:19 ` [PATCH 16/30] The new DWARF indexer Tom Tromey
2021-08-26 2:19 ` [PATCH 17/30] Implement quick_symbol_functions for cooked DWARF index Tom Tromey
2021-08-26 2:19 ` [PATCH 18/30] Wire in the new DWARF indexer Tom Tromey
2021-08-26 2:19 ` [PATCH 19/30] Pre-read DWARF section data Tom Tromey
2021-08-26 2:19 ` [PATCH 20/30] Parallelize DWARF indexing Tom Tromey
2021-08-26 2:19 ` [PATCH 21/30] "Finalize" the DWARF index in the background Tom Tromey
2021-08-26 2:19 ` [PATCH 22/30] Rename write_psymtabs_to_index Tom Tromey
2021-08-26 2:19 ` [PATCH 23/30] Change the key type in psym_index_map Tom Tromey
2021-08-26 2:19 ` [PATCH 24/30] Change parameters to write_address_map Tom Tromey
2021-08-26 2:19 ` [PATCH 25/30] Genericize addrmap handling in the DWARF index writer Tom Tromey
2021-08-26 2:19 ` [PATCH 26/30] Adapt .gdb_index writer to new DWARF scanner Tom Tromey
2021-08-26 2:19 ` [PATCH 27/30] Adapt .debug_names " Tom Tromey
2021-08-26 2:19 ` [PATCH 28/30] Enable the new DWARF indexer Tom Tromey
2021-08-26 2:19 ` [PATCH 29/30] Delete DWARF psymtab code Tom Tromey
2021-08-26 2:19 ` [PATCH 30/30] Remove dwarf2_per_cu_data::v Tom Tromey
2021-08-26 20:32 ` [PATCH 00/30] Rewrite the DWARF "partial" reader Tom de Vries
2021-08-26 21:29 ` Tom Tromey
2021-08-27 7:31 ` Tom de Vries
2021-08-30 15:04 ` Tom Tromey
2021-09-06 19:46 ` Tom Tromey
2021-09-07 10:58 ` Tom de Vries
2021-09-07 12:16 ` Tom de Vries
2021-10-29 23:06 ` Tom Tromey
2021-09-09 19:00 ` Wei-min Pan
2021-09-11 21:08 ` Tom Tromey
2021-09-13 16:50 ` Weimin Pan
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