On 5/23/16 22:30 , David Preece wrote:
> Hi,

Hi,

Apologies no one replied to this sooner.

> I have a zone that's running out of memory (and locking the server, dammit). 
> I noticed the ARC wasn't doing a particularly good job of getting out the way 
> and was wondering, particularly in the age of SSD's, how to limit it's size. 
> All the (solaris) hints I can find say to modify /etc/system but clearly 
> that's not an option for us. Any ideas?

Our general belief is that if you're finding yourself wanting to cap the
ARC, then something else is going on and there's likely a bug we need to
fix. So can you better describe what the sizing of the ARC is and how
it's not getting out of the way? Is there some specific data you can
share here?

> I still maintain that the global zone should stay up regardless of what's 
> going on in the non-globals :( The stall is coming from a debian lx image, I 
> know that Linux has different memory allocation semantics - and the famous 
> OOM killer - but still. I think I'm probably just capping too high - I'm 
> trying to allow system memory minus 1GB for max_physical_memory but at the 
> point at which we stall the ARC is still holding 861MB that would clearly 
> have been useful. Build 20160512T071413Z and image id 
> 473a3a0c-12f2-11e6-acf9-4b8bbe1782ba, if anyone's interested.

Unfortunately I don't think that's going to be a realistic number
because it doesn't take into account the kernel memory that's going to
be allocated on behalf of those zones into that figure. While we can
look at trying to dig into why the ARC isn't releasing more memory, the
amount it has is pretty small, relatively speaking.

When you believe the system is stalling it may help if we can get a dump
of the system so we can see what's going on or dropping into kmdb to
observe why the system seems unresponsive and what's happened. What are
the states of the threads, where is everything spending its time waiting
to happen, etc.

> Oh, one more thing, is there any persistent configuration outside of >
/usbkey?

No, not by default. You can look at boot time modules if you really want
to or other folks use custom scripts after boooting. The /var and /opt
file systems are persistent, but aren't used for much.

Robert


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