gdb is realy slow starting debugging.

Bug #1388999 reported by Søren Holm on 2014-11-03
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
gdb
Unknown
Unknown
gdb (Ubuntu)
Medium
Unassigned

Bug Description

On binaries with a lot of symbols a massive performance degradation has happened between 14.04 and 14.10

I have bisected the gdb performance degradation to this gdb commit

commit 5840bf271c87c3fc14739173fdc91c6a14057130 (refs/bisect/bad)
Author: H.J. Lu <email address hidden>
Date: Wed Jul 16 17:16:24 2014

    Properly match PLT entry against .got.plt relocation

    Relocations against .got.plt section may not be in the same order as
    entries in PLT section. It is incorrect to assume that the Ith reloction
    index against .got.plt section always maps to the (I + 1)th entry in PLT
    section. This patch matches the .got.plt relocation offset/index in PLT
    entry against the index in .got.plt relocation table. It only checks
    R_*_JUMP_SLOT and R_*_IRELATIVE relocations. It ignores R_*_TLS_DESC
    and R_*_TLSDESC relocations since they have different PLT entries.

    bfd/

        PR binutils/17154
        * elf32-i386.c (elf_i386_plt_sym_val): Only match R_*_JUMP_SLOT
        and R_*_IRELATIVE relocation offset with PLT entry.
        * elf64-x86-64.c (elf_x86_64_plt_sym_val): Likewise.
        (elf_x86_64_plt_sym_val_offset_plt_bnd): New.
        (elf_x86_64_get_synthetic_symtab): Use it.

    ld/testsuite/

        PR binutils/17154
        * ld-ifunc/pr17154-i386.d: New file.
        * ld-ifunc/pr17154-x86-64.d: Likewise.
        * ld-ifunc/pr17154-x86.s: Likewise.
        * ld-x86-64/bnd-ifunc-2.d: Likewise.
        * ld-x86-64/bnd-ifunc-2.s: Likewise.
        * ld-x86-64/mpx.exp: Run bnd-ifunc-2.
        * ld-x86-64/tlsdesc-nacl.pd: Updated.
        * ld-x86-64/tlsdesc.pd: Likewise.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: gdb 7.8-1ubuntu4
ProcVersionSignature: Ubuntu 3.16.0-24.32-lowlatency 3.16.4
Uname: Linux 3.16.0-24-lowlatency x86_64
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: KDE
Date: Mon Nov 3 23:27:53 2014
InstallationDate: Installed on 2014-07-11 (115 days ago)
InstallationMedia: Kubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140710)
SourcePackage: gdb
UpgradeStatus: No upgrade log present (probably fresh install)

Søren Holm (sgh) wrote :
Matthias Klose (doko) wrote :

is there a standalone test case for this issue? Also is this issue reported upstream? I can't see any Ubuntu specific patches which would affect this.

Changed in gdb (Ubuntu):
status: New → Incomplete
Matthias Klose (doko) on 2014-12-09
Changed in gdb (Ubuntu):
importance: Undecided → Medium
status: Incomplete → Triaged
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package gdb - 7.8.1-1ubuntu2

---------------
gdb (7.8.1-1ubuntu2) vivid; urgency=medium

  * Fix PR ld/17677, performance regression compared to 7.7.
    LP: #1388999.
 -- Matthias Klose <email address hidden> Tue, 09 Dec 2014 10:25:17 +0100

Changed in gdb (Ubuntu):
status: Triaged → Fix Released
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