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From: matthias.bgg@googlemail.com (Matthias Brugger)
To: kernelnewbies@lists.kernelnewbies.org
Subject: blktrace vs ftrace
Date: Thu, 02 Feb 2012 11:20:07 +0100	[thread overview]
Message-ID: <4F2A6357.3060805@gmail.com> (raw)

Hi all,

I'm trying to analize I/O behavior of Qemu on the host.

I used blktrace and the blk tracer for ftrace but I see different I/O 
behavior.
I use 4 threads in the VM each reading sequentially a file. Readahead is 
turned off. With blktrace reads are transmitted in a sequential way, 
which means the next read will be executed when the first one has 
completed. In comparison with ftrace, up to 4 reads are issued to the 
disk in parallel.

I suppose the different behaviors are due to the overhead introduced by 
the tracers.
My doubt is, which tracer has less influence on the I/O behaviour and 
therefore reflects the system behaviour without tracing.

Thanks a lot,
Matthias

---
http://motzblog.wordpress.com/

             reply	other threads:[~2012-02-02 10:20 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-02 10:20 Matthias Brugger [this message]
2012-02-02 18:15 ` blktrace vs ftrace Mulyadi Santosa
2012-02-02 19:06   ` Matthias Brugger
2012-02-03  5:59     ` Mulyadi Santosa
2012-02-08 10:59       ` Matthias Brugger
2012-02-08 17:04         ` Mulyadi Santosa

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