+2019-11-26 Christian Biesinger <cbiesinger@google.com>
+ Tom Tromey <tom@tromey.com>
+
+ * minsyms.c (minimal_symbol_reader::install): Use
+ parallel_for_each.
+ * gdbsupport/parallel-for.h: New file.
+ * Makefile.in (HFILES_NO_SRCDIR): Add gdbsupport/parallel-for.h.
+
2019-11-26 Christian Biesinger <cbiesinger@google.com>
Tom Tromey <tom@tromey.com>
gdbsupport/common-inferior.h \
gdbsupport/netstuff.h \
gdbsupport/host-defs.h \
+ gdbsupport/parallel-for.h \
gdbsupport/pathstuff.h \
gdbsupport/print-utils.h \
gdbsupport/ptid.h \
--- /dev/null
+/* Parallel for loops
+
+ Copyright (C) 2019 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef GDBSUPPORT_PARALLEL_FOR_H
+#define GDBSUPPORT_PARALLEL_FOR_H
+
+#include <algorithm>
+#if CXX_STD_THREAD
+#include <thread>
+#include "gdbsupport/thread-pool.h"
+#endif
+
+namespace gdb
+{
+
+/* A very simple "parallel for". This splits the range of iterators
+ into subranges, and then passes each subrange to the callback. The
+ work may or may not be done in separate threads.
+
+ 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. */
+
+template<class RandomIt, class RangeFunction>
+void
+parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
+{
+#if CXX_STD_THREAD
+ /* So we can use a local array below. */
+ const size_t local_max = 16;
+ size_t n_threads = std::min (thread_pool::g_thread_pool->thread_count (),
+ local_max);
+ size_t n_actual_threads = 0;
+ std::future<void> futures[local_max];
+
+ 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);
+ size_t elts_per_thread = n_elements / n_threads;
+ n_actual_threads = n_threads - 1;
+ for (int i = 0; i < n_actual_threads; ++i)
+ {
+ RandomIt end = first + elts_per_thread;
+ auto task = [=] ()
+ {
+ callback (first, end);
+ };
+
+ futures[i] = gdb::thread_pool::g_thread_pool->post_task (task);
+ first = end;
+ }
+ }
+#endif /* CXX_STD_THREAD */
+
+ /* Process all the remaining elements in the main thread. */
+ callback (first, last);
+
+#if CXX_STD_THREAD
+ for (int i = 0; i < n_actual_threads; ++i)
+ futures[i].wait ();
+#endif /* CXX_STD_THREAD */
+}
+
+}
+
+#endif /* GDBSUPPORT_PARALLEL_FOR_H */
#include "gdbsupport/symbol.h"
#include <algorithm>
#include "safe-ctype.h"
+#include "gdbsupport/parallel-for.h"
+
+#if CXX_STD_THREAD
+#include <mutex>
+#endif
/* See minsyms.h. */
m_objfile->per_bfd->minimal_symbol_count = mcount;
m_objfile->per_bfd->msymbols = std::move (msym_holder);
+#if CXX_STD_THREAD
+ /* Mutex that is used when modifying or accessing the demangled
+ hash table. */
+ std::mutex demangled_mutex;
+#endif
+
msymbols = m_objfile->per_bfd->msymbols.get ();
- for (int i = 0; i < mcount; ++i)
- {
- if (!msymbols[i].name_set)
- {
- symbol_set_names (&msymbols[i], msymbols[i].name,
- false, m_objfile->per_bfd);
- msymbols[i].name_set = 1;
- }
- }
+ gdb::parallel_for_each
+ (&msymbols[0], &msymbols[mcount],
+ [&] (minimal_symbol *start, minimal_symbol *end)
+ {
+ for (minimal_symbol *msym = start; msym < end; ++msym)
+ {
+ if (!msym->name_set)
+ {
+ /* This will be freed later, by symbol_set_names. */
+ char *demangled_name
+ = symbol_find_demangled_name (msym, msym->name);
+ symbol_set_demangled_name
+ (msym, demangled_name,
+ &m_objfile->per_bfd->storage_obstack);
+ msym->name_set = 1;
+ }
+ }
+ {
+ /* To limit how long we hold the lock, we only acquire it here
+ and not while we demangle the names above. */
+#if CXX_STD_THREAD
+ std::lock_guard<std::mutex> guard (demangled_mutex);
+#endif
+ for (minimal_symbol *msym = start; msym < end; ++msym)
+ {
+ symbol_set_names (msym, msym->name, false,
+ m_objfile->per_bfd);
+ }
+ }
+ });
build_minimal_symbol_hash_tables (m_objfile);
}
free_demangled_name_entry, xcalloc, xfree));
}
-/* Try to determine the demangled name for a symbol, based on the
- language of that symbol. If the language is set to language_auto,
- it will attempt to find any demangling algorithm that works and
- then set the language appropriately. The returned name is allocated
- by the demangler and should be xfree'd. */
+/* See symtab.h */
-static char *
+char *
symbol_find_demangled_name (struct general_symbol_info *gsymbol,
const char *mangled)
{
else
linkage_name_copy = linkage_name;
- gdb::unique_xmalloc_ptr<char> demangled_name_ptr
- (symbol_find_demangled_name (gsymbol, linkage_name_copy.data ()));
+ /* The const_cast is safe because the only reason it is already
+ initialized is if we purposefully set it from a background
+ thread to avoid doing the work here. However, it is still
+ allocated from the heap and needs to be freed by us, just
+ like if we called symbol_find_demangled_name here. */
+ gdb::unique_xmalloc_ptr<char> demangled_name
+ (gsymbol->language_specific.demangled_name
+ ? const_cast<char *> (gsymbol->language_specific.demangled_name)
+ : symbol_find_demangled_name (gsymbol, linkage_name_copy.data ()));
/* Suppose we have demangled_name==NULL, copy_name==0, and
linkage_name_copy==linkage_name. In this case, we already have the
new (*slot) demangled_name_entry
(gdb::string_view (mangled_ptr, linkage_name.length ()));
}
- (*slot)->demangled = std::move (demangled_name_ptr);
+ (*slot)->demangled = std::move (demangled_name);
(*slot)->language = gsymbol->language;
}
else if (gsymbol->language == language_unknown
enum language language,
struct obstack *obstack);
+
+/* Try to determine the demangled name for a symbol, based on the
+ language of that symbol. If the language is set to language_auto,
+ it will attempt to find any demangling algorithm that works and
+ then set the language appropriately. The returned name is allocated
+ by the demangler and should be xfree'd. */
+
+extern char *symbol_find_demangled_name (struct general_symbol_info *gsymbol,
+ const char *mangled);
+
/* Set just the linkage name of a symbol; do not try to demangle
it. Used for constructs which do not have a mangled name,
e.g. struct tags. Unlike SYMBOL_SET_NAMES, linkage_name must
projects / binutils-gdb.git / commitdiff