[Bug 1123272] Re: high cpu usage on download (not optimised SHA256, SHA512, SHA1)

[Oleksij Rempel]

Hi Julian,

I would suggest to rewords you initial comments to some thing like:
"apt was heavy reworked and optimised, probably your initial problem won't hit you as hard as before.
Hashing optimisation can't currently be done for this release without braking the ABI."

Any way, thank you for your work and I hope you can still continue to do it.
Sorry for my misunderstanding.

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Title:
  high cpu usage on download (not optimised SHA256, SHA512, SHA1)

Status in apt package in Ubuntu:
  Confirmed

Bug description:
  http process takes about 20% on intel i5-3317. Here is output of ps aux:
  root      4309 21.7  0.0  37108  2344 pts/2    S+   18:17   0:01 /usr/lib/apt/methods/http

  it can be easy reproduces with "apt-get download firefox-dbg" or any
  other upgrade realted command.

  The reason of this  overhead are this functions:
  22,34%  http  libapt-pkg.so.4.12.0  [.] SHA256_Transform(_SHA256_CTX*, unsigned int const*)
  14,81%  http  libapt-pkg.so.4.12.0  [.] SHA512_Transform(_SHA512_CTX*, unsigned long const*)
  8,11%  http  libapt-pkg.so.4.12.0  [.] SHA1Transform(unsigned int*, unsigned char const*) 
  5,62%  http  libapt-pkg.so.4.12.0  [.] MD5Transform(unsigned int*, unsigned int const*)

  libapt uses own implementation of this hasches without any optimisation.  Are there any reason why libapt do not use
  openssl? Beside current version of openssl has AVX optimised SHA* implementations.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: apt 0.9.7.7ubuntu1
  ProcVersionSignature: Ubuntu 3.8.0-4.9-generic 3.8.0-rc6
  Uname: Linux 3.8.0-4-generic x86_64
  ApportVersion: 2.8-0ubuntu4
  Architecture: amd64
  Date: Tue Feb 12 18:12:33 2013
  InstallationDate: Installed on 2012-09-13 (152 days ago)
  InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120913.1)
  MarkForUpload: True
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: apt
  UpgradeStatus: Upgraded to raring on 2013-02-06 (5 days ago)

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