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* [Bug c++/26491] New: second run of program very slow
@ 2020-08-20 12:39 noelgrandin at gmail dot com
2020-08-24 10:17 ` [Bug c++/26491] " noelgrandin at gmail dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: noelgrandin at gmail dot com @ 2020-08-20 12:39 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26491
Bug ID: 26491
Summary: second run of program very slow
Product: gdb
Version: 9.1
Status: UNCONFIRMED
Severity: minor
Priority: P2
Component: c++
Assignee: unassigned at sourceware dot org
Reporter: noelgrandin at gmail dot com
Target Milestone: ---
Created attachment 12784
--> https://sourceware.org/bugzilla/attachment.cgi?id=12784&action=edit
perf flame graph
version 9.1-5 running on Fedora 32
I am running LibreOffice unit tests.
(e.g. make CppunitTest_chart2_import)
The first time I debug something, I get this
(gdb) r
... starts within 10 seconds....
.. I stop stuff...
... process exits...
(gdb) r
... now it takes 5 mins to get going again ....
This is on a pretty decent box (4Ghz i7)
I attach a flame graph.
I am building with clang, and with
--enable-split-debug
--enable-gdb-index
if that makes any difference.
Funnily, this only seems to apply to the unit tests, the actually main binary
(soffice) is fine.
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* [Bug c++/26491] second run of program very slow
2020-08-20 12:39 [Bug c++/26491] New: second run of program very slow noelgrandin at gmail dot com
@ 2020-08-24 10:17 ` noelgrandin at gmail dot com
2020-08-24 12:03 ` simark at simark dot ca
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: noelgrandin at gmail dot com @ 2020-08-24 10:17 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26491
--- Comment #1 from Noel Grandin <noelgrandin at gmail dot com> ---
Created attachment 12791
--> https://sourceware.org/bugzilla/attachment.cgi?id=12791&action=edit
patch to speed up demangling
This patch reduces the time taken to restart a program by 50%
Yes, the buffer really needs to be this big - C++ symbols in Libreoffice
frequently generate very long demangled names :-)
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* [Bug c++/26491] second run of program very slow
2020-08-20 12:39 [Bug c++/26491] New: second run of program very slow noelgrandin at gmail dot com
2020-08-24 10:17 ` [Bug c++/26491] " noelgrandin at gmail dot com
@ 2020-08-24 12:03 ` simark at simark dot ca
2020-08-24 16:18 ` noelgrandin at gmail dot com
2020-08-24 16:20 ` noelgrandin at gmail dot com
3 siblings, 0 replies; 5+ messages in thread
From: simark at simark dot ca @ 2020-08-24 12:03 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26491
Simon Marchi <simark at simark dot ca> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |simark at simark dot ca
--- Comment #2 from Simon Marchi <simark at simark dot ca> ---
Hi,
We don't do patch review on Bugzilla. Would you mind sending the patch to the
relevant mailing lists?
Since this touches code shared by binutils and gcc, please include the
following mailing lists:
- gdb-patches@sourceware.org
- binutils@sourceware.org
- gcc-patches@gcc.gnu.org
Thanks,
Simon
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* [Bug c++/26491] second run of program very slow
2020-08-20 12:39 [Bug c++/26491] New: second run of program very slow noelgrandin at gmail dot com
2020-08-24 10:17 ` [Bug c++/26491] " noelgrandin at gmail dot com
2020-08-24 12:03 ` simark at simark dot ca
@ 2020-08-24 16:18 ` noelgrandin at gmail dot com
2020-08-24 16:20 ` noelgrandin at gmail dot com
3 siblings, 0 replies; 5+ messages in thread
From: noelgrandin at gmail dot com @ 2020-08-24 16:18 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26491
Noel Grandin <noelgrandin at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
--- Comment #3 from Noel Grandin <noelgrandin at gmail dot com> ---
looks like I was mistaken, and a big chunk of the CPU time was caused by
unwittingly having
MALLOC_PERTURB_
MALLOC_CHECK_
active for gdb itself.
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* [Bug c++/26491] second run of program very slow
2020-08-20 12:39 [Bug c++/26491] New: second run of program very slow noelgrandin at gmail dot com
` (2 preceding siblings ...)
2020-08-24 16:18 ` noelgrandin at gmail dot com
@ 2020-08-24 16:20 ` noelgrandin at gmail dot com
3 siblings, 0 replies; 5+ messages in thread
From: noelgrandin at gmail dot com @ 2020-08-24 16:20 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26491
--- Comment #4 from Noel Grandin <noelgrandin at gmail dot com> ---
thanks to djdelorie for helping me debug that
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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2020-08-20 12:39 [Bug c++/26491] New: second run of program very slow noelgrandin at gmail dot com
2020-08-24 10:17 ` [Bug c++/26491] " noelgrandin at gmail dot com
2020-08-24 12:03 ` simark at simark dot ca
2020-08-24 16:18 ` noelgrandin at gmail dot com
2020-08-24 16:20 ` noelgrandin at gmail dot com
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