[Emacs-bug-tracker] bug#8200: closed (cp -lr uses a lot of CPU time. )

[GNU bug Tracking System]

Your message dated Thu, 10 Mar 2011 18:39:34 +0100
with message-id <address@hidden>
and subject line Re: bug#8200: cp -lr uses a lot of CPU time.
has caused the GNU bug report #8200,
regarding cp -lr uses a lot of CPU time. 
to be marked as done.

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8200: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=8200
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> --- Begin Message ---
>
>
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> Subject: 
>
> cp -lr uses a lot of CPU time. 
>
>
>
>
> Date: 
>
> Tue, 8 Mar 2011 06:08:40 +0100
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>
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> User-agent: 
>
> Mutt/1.5.13 (2006-08-11)
>
>
>
>
> Hi, 
>
> In my backupscripts I need a "cp -lr" every day. I make backups of
> directories that hold up to millions of files. 
>
> When 
>
>         cp -lr sourc dest
>
> runs for a while, it becomes CPU limited. Virtual memory is only about
> 2Mb. "resident" is under 1M.
>
> Top reports: 
>
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND           
> 26721 root      20   0  2456  720  468 R 58.0  0.1  65:32.60 cp
>  2855 root      20   0  2560  936  624 R 40.8  0.1  30:30.52 cp
>
> and I doubt they are half way through.
>
> I wrote an application I call "cplr" which does the obvious in the
> obvious manner, and it doesn't have this problem. 
>
> I've run "strace", and determined that it is not doing systemcalls
> that take much CPU time. Most system calls return in microseconds.
>
> The time spent /between/ system calls runs up into the hundreds of
> milliseconds. You might say: well that's way less than a
> second. Sure. But if you need to do that tens of thousands of times it
> becomes quite significant....
>
>
> So my question is: Why does cp -lr take such rediculous amounts of CPU
> time?
>
> Or another way: BUG REPORT: cp -lr takes unneccessary amounts of CPU
> time.
>
>         Roger. 
>
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> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#8200: cp -lr uses a lot of CPU time.
>
>
>
>
> Date: 
>
> Thu, 10 Mar 2011 18:39:34 +0100
>
>
>
>
> Rogier Wolff wrote:
> > Aaargh... It seems the bug has been fixed... Feel free to ignore my
> > explanation below.
>
> Thanks.  I've marked this ticket as closed.
>
> > On Tue, Mar 08, 2011 at 04:05:04PM +0100, Jim Meyering wrote:
> >> For starters, what version of cp did you use?
> >> Run cp --version
> >
> > -> cp (GNU coreutils) 8.5
>
> In v7.0-63-g3ece035, I made this change:
>
>     http://git.sv.gnu.org/cgit/coreutils.git/commit/?id=3ece0355d52e41a1
>     cp: use far less memory in some cases
>
>     cp --link was "remembering" many name,dev,inode triples unnecessarily.
>     ...
>
> which would make a big difference in your case.
>
>
> --- End Message ---