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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/23710] gdb is slow and memory hungry consuming debug
 generated with LTO by GCC
Date: Sun, 08 Mar 2020 11:09:59 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D23710

--- Comment #11 from Tom de Vries <vries at gcc dot gnu.org> ---
Comparison, cc1 vs cc1.dwz (produced using dwz build from current master
branch):
...
$ diff.sh cc1 cc1.dwz
.debug_info      red: 49.30%    97418416  49399513
.debug_abbrev    red: 42.04%     1699940    985372
.debug_str       red: 0%         6344030   6344030
total            red: 46.21%   105462386  56728915
...

lldb roughly uses same amount of memory, that is: cc1.dwz uses 5.7% less:
...
$ time.sh lldb -batch cc1 -o "b do_rpo_vn"
(lldb) target create "cc1"
Current executable set to 'cc1' (x86_64).
(lldb) b do_rpo_vn
Breakpoint 1: 3 locations.
maxmem: 519116
real: 2.63
user: 4.21
system: 0.14
$ time.sh lldb -batch cc1.dwz -o "b do_rpo_vn"
(lldb) target create "cc1.dwz"
Current executable set to 'cc1.dwz' (x86_64).
(lldb) b do_rpo_vn
Breakpoint 1: 3 locations.
maxmem: 489596
real: 2.78
user: 4.01
system: 0.10
...

With gdb, the difference is a reduction of 51.9%:
...
$ time.sh gdb cc1 -batch -iex "set language c++" -iex "maint set dwarf
max-cache-age 316" -ex "b do_rpo_vn"
Breakpoint 1 at 0xd40e30: do_rpo_vn. (2 locations)
maxmem: 999404
real: 7.03
user: 6.81
system: 0.25
$ time.sh gdb cc1.dwz -batch -iex "set language c++" -iex "maint set dwarf
max-cache-age 316" -ex "b do_rpo_vn"
Breakpoint 1 at 0xd40e30: do_rpo_vn. (2 locations)
maxmem: 481152
real: 6.15
user: 6.09
system: 0.12
...

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