From mboxrd@z Thu Jan  1 00:00:00 1970
From: compudj@krystal.dyndns.org (Mathieu Desnoyers)
Date: Tue, 4 Aug 2009 09:41:26 -0400
Subject: [ltt-dev] Need for zipped traces ?
In-Reply-To: <68119.30361.qm@web63207.mail.re1.yahoo.com>
References: <68119.30361.qm@web63207.mail.re1.yahoo.com>
Message-ID: <20090804134126.GD23807@Krystal>

* Ajit R (ajitrzid at yahoo.com) wrote:
> 
> Hi
>   Just wondering if zipping traces as they are being generated makes sense. This would be useful on embedded targets which could quickly run out of resources.
> 

It could, but it requires extra CPU time while tracing.

I would rather use something based on gzip (zlib1). Using the most
lightweight compression levels should be able to compress one subbuffer
after another without wasting too much resources.

However, with the recent LTTng versions, given we use zero-copy splice
to write to disk, the "easy way" to do it (maybe not the best) is to
write data to a temporary file (which will stay in the buffer cache),
compress it and append it to the tracefile, and clear the temporary
file.

All this can be done by modifying lttd.

Mathieu

> Thanks
> Ajit
> 
> 
>       
> 
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-- 
Mathieu Desnoyers
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