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0b79576c9d
New in v2:
- actually use m_enabled in the constructor and destructor
- output using gdb_stdlog->write_async_safe instead of gdb_printf
scoped_time_it is a small utility that measures and prints how much time
a given thread spent in a given scope. Similar to the time(1) command,
it prints the time spent in user mode, system mode, and the wall clock
time. It also prints the CPU utilization percentage, which is:
(user + sys) / wall
This can help spot cases where the workload is not well balanced between
workers, or the CPU utilization is not optimal (perhaps due to
contention around a lock for example).
To use it, just add it in some scope. For instance, a subsequent patch
adds it here:
workers.add_task ([this, task_count, iter, last] ()
{
scoped_time_it time_it ("DWARF indexing worker");
process_cus (task_count, iter, last);
});
On destruction, if enabled, it prints a line showing the time spent by
that thread, similar to what time(1) prints.
The example above prints this (one line for each worker thread):
Time for "DWARF indexing worker": wall 0.173, user 0.120, sys 0.034, user+sys 0.154, 89.0 % CPU
Time for "DWARF indexing worker": wall 0.211, user 0.144, sys 0.047, user+sys 0.191, 90.5 % CPU
Time for "DWARF indexing worker": wall 0.368, user 0.295, sys 0.057, user+sys 0.352, 95.7 % CPU
Time for "DWARF indexing worker": wall 0.445, user 0.361, sys 0.072, user+sys 0.433, 97.3 % CPU
Time for "DWARF indexing worker": wall 0.592, user 0.459, sys 0.113, user+sys 0.572, 96.6 % CPU
Time for "DWARF indexing worker": wall 0.739, user 0.608, sys 0.115, user+sys 0.723, 97.8 % CPU
Time for "DWARF indexing worker": wall 0.831, user 0.677, sys 0.140, user+sys 0.817, 98.3 % CPU
Time for "DWARF indexing worker": wall 0.949, user 0.789, sys 0.144, user+sys 0.933, 98.3 % CPU
The object is only enabled if per_command_time (controlled by "maint set
per-command time") is true at construction time. I wanted to avoid
adding a new command for now, but eventually if there are too many
scoped_time_it around the code base and we want to be able to enabled
them selectively (e.g. just the ones in the DWARF reader, or in the
symbol searching functions, etc), we could have a dedicated command for
that.
I added this functionality to GDB because it relies on gdb_printf and
per_command_time, but if we ever need it in gdbsupport, I'm sure we
could find a way to put it there.
Change-Id: I5416ac1448f960f44d85f8449943d994198a271e
Approved-By: Tom Tromey <tom@tromey.com>
104 lines
3.0 KiB
C++
104 lines
3.0 KiB
C++
/* Support for GDB maintenance commands.
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Copyright (C) 2013-2025 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef GDB_MAINT_H
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#define GDB_MAINT_H
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#include "gdbsupport/run-time-clock.h"
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#include <chrono>
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struct obj_section;
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struct objfile;
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extern void set_per_command_time (int);
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extern void set_per_command_space (int);
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/* Update the thread pool for the desired number of threads. */
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extern void update_thread_pool_size ();
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/* Records a run time and space usage to be used as a base for
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reporting elapsed time or change in space. */
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class scoped_command_stats
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{
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public:
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explicit scoped_command_stats (bool msg_type);
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~scoped_command_stats ();
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private:
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DISABLE_COPY_AND_ASSIGN (scoped_command_stats);
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/* Print the time, along with a string. */
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void print_time (const char *msg);
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/* Zero if the saved time is from the beginning of GDB execution.
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One if from the beginning of an individual command execution. */
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bool m_msg_type;
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/* Track whether the stat was enabled at the start of the command
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so that we can avoid printing anything if it gets turned on by
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the current command. */
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bool m_time_enabled : 1;
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bool m_space_enabled : 1;
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bool m_symtab_enabled : 1;
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run_time_clock::time_point m_start_cpu_time;
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std::chrono::steady_clock::time_point m_start_wall_time;
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long m_start_space;
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/* Total number of symtabs (over all objfiles). */
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int m_start_nr_symtabs;
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/* A count of the compunits. */
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int m_start_nr_compunit_symtabs;
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/* Total number of blocks. */
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int m_start_nr_blocks;
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};
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/* RAII structure used to measure the time spent by the current thread in a
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given scope. */
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struct scoped_time_it
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{
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/* WHAT is the prefix to show when the summary line is printed. */
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scoped_time_it (const char *what);
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DISABLE_COPY_AND_ASSIGN (scoped_time_it);
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~scoped_time_it ();
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private:
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bool m_enabled;
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/* Summary line prefix. */
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const char *m_what;
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/* User time at the start of execution. */
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user_cpu_time_clock::time_point m_start_user;
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/* System time at the start of execution. */
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system_cpu_time_clock::time_point m_start_sys;
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/* Wall-clock time at the start of execution. */
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std::chrono::steady_clock::time_point m_start_wall;
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};
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extern obj_section *maint_obj_section_from_bfd_section (bfd *abfd,
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asection *asection,
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objfile *ofile);
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#endif /* GDB_MAINT_H */
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