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 Post subject: Memory - Swap - IOWait?
PostPosted: Mon Feb 16, 2009 2:39 am 
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Joined: Fri Nov 21, 2003 10:23 pm
Posts: 66
I just upgraded to R5.5.

I'm using a Dell Optoplex GX270 2.8G P4 for a backend, I do not do any HD.

and 2 Dell optoplex gx150s for frontends

This setup worked well for me under R5F27 but now I am having performance issues on the backend. I was seeing wait times between 50-100%. I was ab le to solve the wait problem by turning off swap. The system will now run for days without the wait going over 10% but I have occasional out of memory issues so I added 256M of ram bringing the total to 768 only to watch it all go to cache within 10 min of starting to watch tv. How can I limit the cache?

It really doesn't seem to make sense to me to cache video that is being played or am I missing something.


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PostPosted: Mon Feb 16, 2009 1:45 pm 
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Joined: Thu Mar 25, 2004 11:00 am
Posts: 9551
Location: Arlington, MA
Linux is supposed to use as much of your memory as possible, that's what RAM is for after all. On the other hand it's supposed to use it in a way that lets it be released when it's needed for something else.

The real problem is that there is a memory leak between the FE and the Nvidia X driver which eventually causes a problem. This is covered in the R5.5 Hints. There still isn't a real fix available yet, but there are a couple simple workarounds documented there. (Known Issues 2.3.2)


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PostPosted: Mon Feb 16, 2009 3:52 pm 
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Joined: Fri Nov 21, 2003 10:23 pm
Posts: 66
Thanks tjc, I agree with what you say in general but wonder about caching video files and causing swap. Ironically, if I understand what is happening, the file is chewing up cache on the backend machine which doesn't do the remote frontend that is playing it any good. I'll admit here that I don't really understand the mechanisms behind the NFS.


The situation seems to be under control with the additional ram so I guess the upgrade to R5.5 just pushed my systems resources to the breaking point (this setup has worked well under R5F27). I didn't think Myth needed that much ram but it does just keep growing doesn't it.


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