Perl slowness

[Dotan Shavit]

On Tuesday 08 September 2009, Noam Rathaus wrote:
> So I am stuck
>
> Grrr
>
> Anyone with ideas on how I can understand why "my packages" are causing
> issues, while apparently, "perl-provided" packages such as LWP::UserAgent
> dont?
http://www.gksoft.com/a/fun/catch-lion.html

>
> On Tue, Sep 8, 2009 at 5:58 PM, Shachar Shemesh <shachar at shemesh.biz> wrote:
> >  Noam Rathaus wrote:
> >
> > The only obvious one is that read() shown under strace, takes a
> > significant more time on the new machine than the old one
> >
> > You can split the difference between the platforms into three groups:
> > Time spent in the kernel (0.032 seconds)
> > Time spent in userspace (7.761 seconds)
> > Time spent sleeping or otherwise scheduled out (7.287 seconds)
> >
> > strace -c goes a long way, and works very hard, to show us information
> > that is not useful to us. It counts CPU time spent in system calls, not
> > actual wall time. What may provide a more useful output in this case is
> > -T, which will also count time in which the process was sleeping inside a
> > system call (which accounts for about half the slowdown).
> >
> > The second half of the slowdown, the one done in user space, is more
> > difficult to trace without the sources (i.e. - the perl sources).
> > valgrind has a module for detecting what causes a slowdown, but I doubt
> > Noam wants to start analyzing perl to figure out what the different areas
> > actually mean.
> >
> >
> > Shachar
> >
> > On Tue, Sep 8, 2009 at 5:43 PM, Shachar Shemesh 
<shachar at shemesh.biz>wrote:
> >>  Noam Meltzer wrote:
> >>
> >> the time output does looks like you have higher cpu usage for some
> >> reason, so i agree with Shachar on this.
> >>
> >> you can also try to pinpoint the place the cpu is spent.
> >> strace and/or ltrace with the '-f -c' flags can help.
> >>
> >>  I'm not sure about ltrace, but strace will not help. Most of the time
> >> is spent in user space, not in the kernel.
> >>
> >> Strace may help if the problem is time spent in another process (i.e. -
> >> while the main process is sleeping), but it seems Noam has already tried
> >> that one and failed to spot any obvious candidates.
> >>
> >> Shachar
> >>
> >> On Tue, Sep 8, 2009 at 5:24 PM, Shachar Shemesh 
<shachar at shemesh.biz>wrote:
> >>>  Noam Rathaus wrote:
> >>>
> >>> I know the time difference doesn't look too bad, but take a bigger code
> >>> set:
> >>>
> >>> Fast:
> >>> real    0m1.682s
> >>> user    0m1.584s
> >>> sys    0m0.064s
> >>>
> >>> Slow:
> >>> real    0m16.730s
> >>> user    0m9.345s
> >>> sys    0m0.096s
> >>>
> >>>   These times spell "CPU intensive". Does your library do anything
> >>> special? If you try to import a dummy library, does this still happen?
> >>>
> >>> Shachar
> >>>
> >>> --
> >>> Shachar Shemesh
> >>> Lingnu Open Source Consulting Ltd.http://www.lingnu.com
> >>
> >> --
> >> Shachar Shemesh
> >> Lingnu Open Source Consulting Ltd.http://www.lingnu.com
> >
> > --
> > Shachar Shemesh
> > Lingnu Open Source Consulting Ltd.http://www.lingnu.com