Re: Bad fs performance, IO freezes

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-10-26 22:00, cheater00 . wrote:
> Hello,
> currently my computer freezes every several seconds for half a second
> or so. Using it feels like I'm playing musical chairs with the kernel.
> I have just one download happening on utorrent right now - this is
> what the graph looks like:
> http://i.imgur.com/LqhMtrJ.png
> and every time a new spike happens, a freeze happens just before
> that... that's the only time those freezes happen, too.
>
Do you have the 'autodefrag' mount option enabled?  If it is turned on, 
then that may be the problem.  Most bittorrent clients pre-allocate the 
space for a download, then write each block directly into the location 
it's supposed to be in the resultant download, which means depending on 
how it's pre-allocating the space, that you end up with a large number 
of randomly ordered writes into a single file, which in turn will 
trigger the autodefrag code, which can cause latency spikes when you're 
also hitting the disk at the same time.


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