/usr/bin/script eating 100% cpu with portupgrade and xargs

[Jeremy Chadwick]

On Sun, Sep 18, 2011 at 12:54:13AM -0400, Jason Hellenthal wrote:
> On Sun, Sep 18, 2011 at 01:49:15AM +0200, Ronald Klop wrote:
> > Hi,
> > 
> > I'm running portupgrade in screen to update all the ports for  
> > 9-BETA2/9-CURRENT on amd64. While doing this script eats 100% cpu.
> > Because portupgrade -fa crashed I'm running this command to update the  
> > remaining non-updates ports.
> > find /var/db/pkg -name +DESC -mtime +2 |cut -d / -f 5 | xargs time nice -n  
> > 20 portupgrade -f
> > 
> > The output of truss -p `pgrep script` is this:
> > clock_gettime(13,{1316301104.000000000 })        = 0 (0x0)
> > select(5,{0 4},0x0,0x0,{30.000000 })             = 1 (0x1)
> > read(0,0x7fffffffcdf0,1024)                      = 0 (0x0)
> > write(4,0x7fffffffcdf0,0)                        = 0 (0x0)
> > clock_gettime(13,{1316301104.000000000 })        = 0 (0x0)
> > select(5,{0 4},0x0,0x0,{30.000000 })             = 1 (0x1)
> > read(0,0x7fffffffcdf0,1024)                      = 0 (0x0)
> > write(4,0x7fffffffcdf0,0)                        = 0 (0x0)
> > clock_gettime(13,{1316301104.000000000 })        = 0 (0x0)
> > select(5,{0 4},0x0,0x0,{30.000000 })             = 1 (0x1)
> > read(0,0x7fffffffcdf0,1024)                      = 0 (0x0)
> > write(4,0x7fffffffcdf0,0)                        = 0 (0x0)
> > clock_gettime(13,{1316301104.000000000 })        = 0 (0x0)
> > select(5,{0 4},0x0,0x0,{30.000000 })             = 1 (0x1)
> > read(0,0x7fffffffcdf0,1024)                      = 0 (0x0)
> > write(4,0x7fffffffcdf0,0)                        = 0 (0x0)
> > 
> > So it is really fast in reading and writing 0 bytes most of the time.
> > 
> > I also found http://web.archiveorange.com/archive/v/6ETvLvjo60Gj9geAUAb6  
> > and I think I am better of by rewriting my command so stdin/stdout is  
> > still the terminal. Although the link is a couple of years old.
> > 
> > Is this known? Can somebody explain me why my xargs command is not working  
> > well?
> > 
> 
> Are you absolutely sure that its script(1) causing this ? 100% CPU usage
> has been a known side effect of screen(1) for quite some time. Rebuild
> it and try again.

Jason's referring to this, I believe:
http://www.freebsd.org/cgi/cvsweb.cgi/ports/sysutils/screen/Makefile#rev1.55

To clarify the what the commit message means: it does not mean "when the
package is installed the installation takes up 100% CPU".  It means
"once the package is installed and screen is used, screen takes up 100%
CPU".  I know because I've seen this behaviour in the past (one of the
many, many reasons I build ports from source).

However:
http://www.freebsd.org/cgi/cvsweb.cgi/ports/sysutils/screen/Makefile#rev1.78

So: If a binary package is being installed through your above
portupgrade command, and you're seeing this problem, then it sounds to
me like commit revision 1.78 is a regression and NO_PACKAGE should be
put back into place + packages removed from all mirrors.

There are many reasons to not use GNU screen at all, or if you must have
something like it, use tmux.  I recently had to provide an analysis of
how GNU screen destroys one's terminal[1]; so if the above problem turns
out to be caused by GNU screen as well, I'll just add it to my
ever-growing list of reasons the software should be nuked from orbit.

Otherwise, if this turns out to be a problem with portupgrade (which you
found some evidence supporting such), then the solution is simple: stop
using portupgrade, use portmaster (if it lacks things you need ask Doug
Barton, he's incredibly receptive to adding new features/fixing things).
Two databases that aren't compatible, ruby shims, and other crap = not
worth it.  Think the database ordeal is long over with/fixed/whatever?
It isn't[2].

[1]: http://lists.freebsd.org/pipermail/freebsd-stable/2011-June/063052.html
[2]: http://www.dslreports.com/forum/r26304856-FreeBSD-defining-portmaster-alias

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, US |
| Making life hard for others since 1977.               PGP 4BD6C0CB |