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The python code maintains a list of threads for each inferior. This list is implemented as a linked list. When the number of threads grows high, this implementation can begin to be a performance bottleneck as finding a particular thread_object in the list has a complexity of O(N). We see this in ROCgdb[1], a downstream port of GDB for AMDGUP. On AMDGPU devices, the number of threads can get significantly higher than on usual GDB workloads. In some situations, we can reach the end of the inferior process with GDB still having a substantial list of known threads. While running target_mourn_inferior, we end up in inferior::clear_thread_list which iterates over all remaining threads and marks each thread exited. This fires the gdb::observers::thread_exit observer and eventually py-inferior.c:set_thread_exited gets called. This function searches in the linked list with poor performances. This patch proposes to change the linked list that keeps the per inferior_object list of thread_objects into a std::unordered_map. This allows to have the search operation complexity be O(1) on average instead of O(N). With this patch, we can complete clear_thread_list in about 2.5 seconds compared to 10 minutes without it. Except for the performance change, no user visible change is expected. Regression tested on Ubuntu-22.04 x86_64. [1] https://github.com/ROCm-Developer-Tools/ROCgdb
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.