possible regression?

[Greg Freemyer]

Mulyadi,

You disappoint me. ;(

Just kidding, but discussing dd throughput without the
"conv=fdatasync" parameter is just a waste of everyone's time.

And Mag, use a big enough count that it at least takes a few seconds
to complete.  A tenth of a second or less is just way to short to use
as a benchmark.

Greg

On Thu, Jan 20, 2011 at 12:28 AM, Mulyadi Santosa
<mulyadi.santosa at gmail.com> wrote:
> Hi...
>
> On Thu, Jan 20, 2011 at 10:36, Mag Gam <magawake at gmail.com> wrote:
>> Running on Redhat 5.1 if I do,
>
> Are you sure you're using that archaic distro? Or are you talking
> about RHEL 5.1?
>
>> dd bs=1024 count=1000000 if=/dev/zero of=/dev/null
>>
>> I get around 30Gb/sec
>
> Hm, mine is:
> $ dd bs=1024 count=1000000 if=/dev/zero of=/dev/null
> 1000000+0 records in
> 1000000+0 records out
> 1024000000 bytes (1.0 GB) copied, 1.12169 seconds, 913 MB/s
>
> This is on 2.6.36 SMP kernel compiled with gcc version 4.1.2 20080704
> (Red Hat 4.1.2-48).
>
>>
>> However, when I do this with 2.6.37 I get close to 5GB/sec
>
> what if you use another blocksize, let's say 4K or even 32K? here's
> mine (again):
> $ dd bs=4K count=1000000 if=/dev/zero of=/dev/null
> 1000000+0 records in
> 1000000+0 records out
> 4096000000 bytes (4.1 GB) copied, 1.31167 seconds, 3.1 GB/s
>
> $ dd bs=32K count=1000000 if=/dev/zero of=/dev/null
> 1000000+0 records in
> 1000000+0 records out
> 32768000000 bytes (33 GB) copied, 4.91775 seconds, 6.7 GB/s
>
> see the difference?
>
> IMHO it's a matter of what I call "block merge efficiency"....the more
> you stuff pages (that fits into a "magic" number), the faster I/O you
> got.
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>



-- 
Greg Freemyer
Head of EDD Tape Extraction and Processing team
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
CNN/TruTV Aired Forensic Imaging Demo -
   http://insession.blogs.cnn.com/2010/03/23/how-computer-evidence-gets-retrieved/

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com