Bug 137200

Summary: RHEL4 U1: collapse_path patch for gcc
Product: Red Hat Enterprise Linux 4 Reporter: Robert Perkins <rperkins>
Component: gccAssignee: Jakub Jelinek <jakub>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: 4.0CC: aoliva, bkoz, jakub, rth, tao
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
URL: IT_29227
Whiteboard: Tools
Fixed In Version: RHBA-2006-0509 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2006-08-10 21:28:09 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 181409    
Attachments:
Description Flags
squeeze absolute paths into canonical form none

Description Robert Perkins 2004-10-26 17:31:20 UTC 
1. Feature:
Feature Name:  Include provided collapse_path patch for gcc

2. More Detailed Description
  Client requests that we include the provided collapse_path patch for gcc. The
patch is to rework the relative paths in the compilation to be absolute
(/a/b/../c -> /a/c). These relative paths can be a problem in AFS and
potentially NFS environments.

  Architectures (mark all that apply)
   32-bit x86                  X
   64-bit Itanium2             X
   64-bit AMD64/Intel EM64T    X
   64-bit IBM POWER            *
   31-bit IBM S/390            *
   64-bit IBM zSeries          *

X - Required
* - Client doesn't use at present, but this patch should be generic.

  Dependencies: None
  External links: None
  Priority (H,M,L): M
  Target Releases: RHEL3 U5, RHEL4 GA/U1
  Target Release Date: See above
  Drivers or hardware dependency: None
  Target Kernel: N/A

3. Business Justification: Including this patch will make the relocation and
deployment of the compiler much easier for clients in AFS environments.

4. Code Status: Done by client, not submitted/accepted upstream. Would require
us to get upstream acceptance.

5. Hardware to Red Hat? N/A

6. Partner management contact, email, phone, chat: Mike Herron, mherron
Comment 2 Robert Perkins 2004-10-26 17:36:26 UTC 
Request from PM:
Can the tools team please
a) state if they know of an alternate solution.
b) provide any insight in the work that happened upstream (rumored).
c) provide a design estimate for making these patches acceptable to upstream,
and integrating them into RHEL3 as well.
d) list any reasons why this is a really bad idea.
We may want to have a short call with the customer to discuss engineer to engineer.
Comment 7 Stan Cox 2005-09-29 13:27:29 UTC 
Created attachment 119420 [details]
squeeze absolute paths into canonical form
Comment 8 Benjamin Kosnik 2005-09-29 18:08:48 UTC 
Jakub, I think performance is a huge deal! Especially since there has been a lot
of work to improve compilation performance in gcc: I cannot imagine something
that slows down compilation around 10% (or more) to ever get into mailine.
People are mad enough over the creeping compile times.

Walking up a directory tree and lsating for each .. seems to me to be a
performance killer. Ouch!
Comment 12 Jakub Jelinek 2005-09-29 18:23:26 UTC 
I don't think gcc driver ever shows on the radar performance-wise.
For a simple hello world program, GCC driver calls ~ 80 stat/lstat/access
syscalls.  If we cached the info, this could add another 20 or so, even if not,
stat/lstat are fairly cheap when kernel has the dentry loaded (which it has
most of the time).

But from #9 it seems even what I was proposing wouldn't help to the customer.
Collapsing disregarding symlinks is something completely else though,
that is a clear behavioural change, not working around buggy filesystems.
And I don't think that's desirable, at least not desirable by default.
There could perhaps be a GCC switch that would request the different behaviour.
Comment 27 Bob Johnson 2006-04-11 16:18:46 UTC 
This issue is on Red Hat Engineering's list of planned work items 
for the upcoming Red Hat Enterprise Linux 4.4 release.  Engineering 
resources have been assigned and barring unforeseen circumstances, Red 
Hat intends to include this item in the 4.4 release.
Comment 32 Red Hat Bugzilla 2006-08-10 21:28:14 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2006-0509.html