Perl slowness

[Arie Skliarouk]

Hi,

Interesting riddle...

2009/9/8 Noam Rathaus <noamr at beyondsecurity.com>

> The most notable difference is the read time on files (new HD)
> 0.047210 read(7, " <= 0)\n {\n  $numLimit = 10;\n }\n\n "..., 4096)
>
> Instead of (old HW)
> 0.001462 read(6, "owItem = $1;\n\n my $RowItems = $s"..., 4096) = 4096
>
> That is 40 times slower (it is the same file being opened)
>

What is the filesystem used on the machines? Do they have similar mount
flags (no_atime or such)?
If both are ext2/3, compare "tune2fs -l /dev/sda1" on them.
Try to mount both filesystems using noatime and compare timings then.

Full disk might affect fragmentation or placement of the files and thus
require long seeks. As atime needs to be updated (or journal log), buffering
in memory would not help.
Test write speed of the disks.

--
Arie

>
> I have no idea why there is such a difference
>
> hdparm on the old:
> hdparm -t /dev/sda
>
> /dev/sda:
>  Timing buffered disk reads:  190 MB in  3.02 seconds =  62.87 MB/sec
>
> hdparm on the new:
> # hdparm -t /dev/sda
>
> /dev/sda:
>  Timing buffered disk reads:  314 MB in  3.01 seconds = 104.22 MB/sec
>
> On Tue, Sep 8, 2009 at 3:02 PM, Noam Meltzer <tsnoam at gmail.com> wrote:
>
>> Did you try to check with strace ?
>>
>> 2009/9/8 Noam Rathaus <noamr at beyondsecurity.com>
>>
>>> Hi,
>>>
>>>
>>> I have two machines, their hardware is not identical, but their
>>> installation is.
>>>
>>> One is a 3 years old DELL server, while the other is a 1 year old server.
>>>
>>> One is running 2.6.26-2-686 while the other 2.6.30-1-686
>>>
>>> What I am seeing is slow startup - emphasis on startup, the code works
>>> fast once its running - of perl scripts
>>>
>>> Even the smallest perl script such as this:
>>> ===
>>> #!/usr/bin/perl
>>>
>>> use lib '/usr/local/MySystem/lib';
>>>
>>> use DB;
>>>
>>> ===
>>>
>>> Take 7 seconds to start, in comparison to 0.030secods
>>>
>>> If I don't use the "use DB;" which my package
>>>
>>> It loads fast
>>>
>>> I am trying to figure out why, I checked the HD speeds via hdparam, the
>>> newer server is 1.5 times faster 103MB/sec
>>>
>>> I tried to see what libraries were being used, used strace, but I can't
>>> see something "big" that is causing the delay.
>>>
>>> The "use DB;" can be replaced with any other "custom" library package I
>>> wrote, they all take 2-7 seconds to load, while on the other machine it
>>> takes negligible time
>>>
>>> Does someone have a "thread" to cling to?
>>>
>>> Thanks,
>>> Noam Rathaus
>>>
>>> _______________________________________________
>>> Linux-il mailing list
>>> Linux-il at cs.huji.ac.il
>>> http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
>>>
>>>
>>
>
> _______________________________________________
> Linux-il mailing list
> Linux-il at cs.huji.ac.il
> http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.cs.huji.ac.il/pipermail/linux-il/attachments/20090908/203e47a0/attachment-0001.html>