[CentOS] pdflush kernel thread pops up every 10 seconds or so and video decoding grinds to a halt for 1/2 a second

Toby Bluhm toby.bluhm at alltechmedusa.com
Tue Oct 19 15:48:06 EDT 2010


On 10/19/2010 3:34 PM, Aleksey Tsalolikhin wrote:
> On Mon, Oct 18, 2010 at 9:08 PM, JohnS<jses27 at gmail.com>  wrote:
>>
>> On Mon, 2010-10-18 at 18:25 -0700, Aleksey Tsalolikhin wrote:
>>> Hi. A friend of mine was doing real-time video decoding on
>>> Fedora Core 13 and he had a performance glitch (1/2 a second
>>> freeze) every 5-10 seconds.  "top" showed flush-253:0
>>> process at the moment of the freeze.
>>
>> And what is the Priority of it running at?  How many Cores also?
>
> He sees this issue at normal priority and at nice -n -19 / -20.
>
> He has 6 cores with hyperthreading on
>
> 3.8 Ghz, the memory is 1.850 Mhz
>
> The system is 980x Intel 6 core
>
> He just told me he has two modes for his decoding program, in one
> mode the system does not write to disk at all, and there are NO GLITCHES
> doing it this way; another way, it writes lots of little files as it decodes,
> and the glitch happens actually every 5-20 seconds.
>
> Would like to get to the bottom of this so he can decode with temp files
> and without glitches.
>


Ext3 filesystem? Maybe altering the commit option at mount time would help:

http://www.mjmwired.net/kernel/Documentation/filesystems/ext3.txt#49



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