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20a26f4e01
After DWARF has been scanned, the cooked index code does a
"finalization" step in a worker thread. This step combines all the
index entries into a single master list, canonicalizes C++ names, and
splits Ada names to synthesize package names.
While this step is run in the background, gdb will wait for the
results in some situations, and it turns out that this step can be
slow. This is PR symtab/29105.
This can be sped up by parallelizing, at a small memory cost. Now
each index is finalized on its own, in a worker thread. The cost
comes from name canonicalization: if a given non-canonical name is
referred to by multiple indices, there will be N canonical copies (one
per index) rather than just one.
This requires changing the users of the index to iterate over multiple
results. However, this is easily done by introducing a new "chained
range" class.
When run on gdb itself, the memory cost seems rather low -- on my
current machine, "maint space 1" reports no change due to the patch.
For performance testing, using "maint time 1" and "file" will not show
correct results. That approach measures "time to next prompt", but
because the patch only affects background work, this shouldn't (and
doesn't) change. Instead, a simple way to make gdb wait for the
results is to set a breakpoint.
Before:
$ /bin/time -f%e ~/gdb/install/bin/gdb -nx -q -batch \
-ex 'break main' /tmp/gdb
Breakpoint 1 at 0x43ec30: file ../../binutils-gdb/gdb/gdb.c, line 28.
2.00
After:
$ /bin/time -f%e ./gdb/gdb -nx -q -batch \
-ex 'break main' /tmp/gdb
Breakpoint 1 at 0x43ec30: file ../../binutils-gdb/gdb/gdb.c, line 28.
0.65
Regression tested on x86-64 Fedora 34.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29105
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.