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* [Bug gdb/31494] New: gcore should generate sparse cores
@ 2024-03-15 15:34 pedro at palves dot net
2024-03-15 15:34 ` [Bug gdb/31494] " pedro at palves dot net
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: pedro at palves dot net @ 2024-03-15 15:34 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
Bug ID: 31494
Summary: gcore should generate sparse cores
Product: gdb
Version: unknown
Status: NEW
Severity: normal
Priority: P2
Component: gdb
Assignee: unassigned at sourceware dot org
Reporter: pedro at palves dot net
Target Milestone: ---
As can be seen with the gdb.base/bigcore.exp program:
$ gdb -q --batch ./testsuite/outputs/gdb.base/bigcore/bigcore -ex "run" -ex
"gcore /tmp/core.gdb"
(...)
Dump core ....
Program received signal SIGSEGV, Segmentation fault.
main () at gdb.base/bigcore.c:270
270 *(volatile char*)0 = 0;
warning: Memory read failed for corefile section, 4096 bytes at
0xffffffffff600000.
Saved corefile /tmp/core.gdb
$ du --hu /tmp/core.gdb
16G /tmp/core.gdb
$ du --hu --apparent-size /tmp/core.gdb
16G /tmp/core.gdb
... GDB isn't generating sparse core files. It would good if it did.
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* [Bug gdb/31494] gcore should generate sparse cores
2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
@ 2024-03-15 15:34 ` pedro at palves dot net
2024-03-15 15:35 ` [Bug corefiles/31494] " pedro at palves dot net
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pedro at palves dot net @ 2024-03-15 15:34 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
Pedro Alves <pedro at palves dot net> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at sourceware dot org |pedro at palves dot net
--- Comment #1 from Pedro Alves <pedro at palves dot net> ---
I've got a patch.
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* [Bug corefiles/31494] gcore should generate sparse cores
2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
2024-03-15 15:34 ` [Bug gdb/31494] " pedro at palves dot net
@ 2024-03-15 15:35 ` pedro at palves dot net
2024-03-15 18:32 ` pedro at palves dot net
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pedro at palves dot net @ 2024-03-15 15:35 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
Pedro Alves <pedro at palves dot net> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|gdb |corefiles
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* [Bug corefiles/31494] gcore should generate sparse cores
2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
2024-03-15 15:34 ` [Bug gdb/31494] " pedro at palves dot net
2024-03-15 15:35 ` [Bug corefiles/31494] " pedro at palves dot net
@ 2024-03-15 18:32 ` pedro at palves dot net
2024-03-22 12:31 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pedro at palves dot net @ 2024-03-15 18:32 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
--- Comment #2 from Pedro Alves <pedro at palves dot net> ---
https://inbox.sourceware.org/gdb-patches/20240315182705.4064062-1-pedro@palves.net/T/#u
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* [Bug corefiles/31494] gcore should generate sparse cores
2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
` (2 preceding siblings ...)
2024-03-15 18:32 ` pedro at palves dot net
@ 2024-03-22 12:31 ` cvs-commit at gcc dot gnu.org
2024-03-22 12:34 ` pedro at palves dot net
2024-03-22 15:33 ` tromey at sourceware dot org
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-03-22 12:31 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
--- Comment #3 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=431a6b091d3106bc9750d82f50535d35d760f920
commit 431a6b091d3106bc9750d82f50535d35d760f920
Author: Pedro Alves <pedro@palves.net>
Date: Fri Mar 22 12:31:29 2024 +0000
Teach GDB to generate sparse core files (PR corefiles/31494)
This commit teaches GDB's gcore command to generate sparse core files
(if supported by the filesystem).
To create a sparse file, all you have to do is skip writing zeros to
the file, instead lseek'ing-ahead over them.
The sparse logic is applied when writing the memory sections, as
that's where the bulk of the data and the zeros are.
The commit also tweaks gdb.base/bigcore.exp to make it exercise
gdb-generated cores in addition to kernel-generated cores. We
couldn't do that before, because GDB's gcore on that test's program
would generate a multi-GB non-sparse core (16GB on my system).
After this commit, gdb.base/bigcore.exp generates, when testing with
GDB's gcore, a much smaller core file, roughly in line with what the
kernel produces:
real sizes:
$ du --hu testsuite/outputs/gdb.base/bigcore/bigcore.corefile.*
2.2M testsuite/outputs/gdb.base/bigcore/bigcore.corefile.gdb
2.0M testsuite/outputs/gdb.base/bigcore/bigcore.corefile.kernel
apparent sizes:
$ du --hu --apparent-size
testsuite/outputs/gdb.base/bigcore/bigcore.corefile.*
16G testsuite/outputs/gdb.base/bigcore/bigcore.corefile.gdb
16G testsuite/outputs/gdb.base/bigcore/bigcore.corefile.kernel
Time to generate the core also goes down significantly. On my machine, I
get:
when writing to an SSD, from 21.0s, down to 8.0s
when writing to an HDD, from 31.0s, down to 8.5s
The changes to gdb.base/bigcore.exp are smaller than they look at
first sight. It's basically mostly refactoring -- moving most of the
code to a new procedure which takes as argument who should dump the
core, and then calling the procedure twice. I purposely did not
modernize any of the refactored code in this patch.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31494
Reviewed-By: Lancelot Six <lancelot.six@amd.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: John Baldwin <jhb@FreeBSD.org>
Change-Id: I2554a6a4a72d8c199ce31f176e0ead0c0c76cff1
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* [Bug corefiles/31494] gcore should generate sparse cores
2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
` (3 preceding siblings ...)
2024-03-22 12:31 ` cvs-commit at gcc dot gnu.org
@ 2024-03-22 12:34 ` pedro at palves dot net
2024-03-22 15:33 ` tromey at sourceware dot org
5 siblings, 0 replies; 7+ messages in thread
From: pedro at palves dot net @ 2024-03-22 12:34 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
Pedro Alves <pedro at palves dot net> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #4 from Pedro Alves <pedro at palves dot net> ---
Patch merged to master.
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* [Bug corefiles/31494] gcore should generate sparse cores
2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
` (4 preceding siblings ...)
2024-03-22 12:34 ` pedro at palves dot net
@ 2024-03-22 15:33 ` tromey at sourceware dot org
5 siblings, 0 replies; 7+ messages in thread
From: tromey at sourceware dot org @ 2024-03-22 15:33 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31494
Tom Tromey <tromey at sourceware dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |tromey at sourceware dot org
Target Milestone|--- |15.1
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2024-03-15 15:34 [Bug gdb/31494] New: gcore should generate sparse cores pedro at palves dot net
2024-03-15 15:34 ` [Bug gdb/31494] " pedro at palves dot net
2024-03-15 15:35 ` [Bug corefiles/31494] " pedro at palves dot net
2024-03-15 18:32 ` pedro at palves dot net
2024-03-22 12:31 ` cvs-commit at gcc dot gnu.org
2024-03-22 12:34 ` pedro at palves dot net
2024-03-22 15:33 ` tromey at sourceware dot org
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