Perl slowness

[Noam Rathaus]

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?

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
>
>
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