touch-packages team mailing list archive

[Søren Holm <sgh@xxxxxx>]

Public bug reported:

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 <hjl.tools@xxxxxxxxx>
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)

** Affects: gdb (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug utopic

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https://bugs.launchpad.net/bugs/1388999

Title:
  gdb is realy slow starting debugging.

Status in “gdb” package in Ubuntu:
  New

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 <hjl.tools@xxxxxxxxx>
  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)

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