Re: Tracking actual disk write sources instead of flush thread

[Phillip Susi <psusi@ubuntu.com>]

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On 4/16/2014 1:44 PM, Zuckerman, Boris wrote:
> Typically File System services do not offer semantics of 
> transactional isolation. Attempts to add that took place and were 
> rejected. Therefore, we are speaking only about some potential 
> performance penalty, right?

Not at all.  This has nothing to do with transactions; it is simply a
question of being able to identify what process is causing all of the
disk IO, like via iotop.  By counting writes in the process that
initiates the writeout of dirty pages, rather than the process that
dirties the page, it renders the write io tracking largely inaccurate
to the point of being useless at times, since often the process
dirtying the pages, even with an actual write() system call, is not
the process that initiates the writeout.

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