[Bug symtab/29105] new DWARF reader still slow

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29105

--- Comment #9 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=20a26f4e018cd0cb40a3b81568be0d4f164eed0f

commit 20a26f4e018cd0cb40a3b81568be0d4f164eed0f
Author: Tom Tromey <tromey@adacore.com>
Date:   Fri May 13 13:46:52 2022 -0600

    Finalize each cooked index separately

    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

-- 
You are receiving this mail because:
You are on the CC list for the bug.