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From: Phillip Susi <psusi@ubuntu.com>
To: linux-btrace@vger.kernel.org
Subject: Re: Events out of order
Date: Wed, 31 Dec 2014 15:09:22 +0000	[thread overview]
Message-ID: <54A411A2.1060605@ubuntu.com> (raw)
In-Reply-To: <54A355D2.5060704@ubuntu.com>

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On 12/31/2014 9:58 AM, Chris Mason wrote:
> It's been a while since I looked at this, but looks like blkparse
> has a pipeline mode and a more exact mode.  In pipeline mode, it's
> really trying to get data to the screen quickly and without using a
> huge amount of resources.  In order to put things in order, it
> would need to buffer the entire stream before outputting anything.
> So instead it works in chunks, which is what you're seeing.

Makes sense; it would be nice if the man page mentioned this drawback.

> It enables pipeline mode when the input file from -i is a pipe.
> You'll get better results if you allow blktrace to output into a
> collection of files and pass the prefix to blkparse.
> 
> instead of blktrace -o - use blktrace -o prefix ; blkparse -i
> prefix
> 
> For multiple devices, iowatcher uses a directory to store all of
> them, which is easier.
> 
> If you really want a single file result, take the per-cpu files
> from blktrace, run them through blkparse and add -d dumpfile, which
> will sort and pack all the results into a single binary file.  It's
> compressable and you can then delete all the per-cpu files.

Thanks; I thought I read something like that at one point but couldn't
find it in the man page last night.


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  parent reply	other threads:[~2014-12-31 15:09 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-31  1:48 Events out of order Phillip Susi
2014-12-31  1:51 ` Phillip Susi
2014-12-31  1:53 ` Alireza Haghdoost
2014-12-31  3:23 ` Phillip Susi
2014-12-31  4:29 ` Alireza Haghdoost
2014-12-31 14:36 ` Phillip Susi
2014-12-31 14:58 ` Chris Mason
2014-12-31 15:09 ` Phillip Susi [this message]
2014-12-31 15:19 ` Jens Axboe

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