zfs + uma

[Robert N. M. Watson]

On 18 Sep 2010, at 12:27, Andriy Gapon wrote:

> on 18/09/2010 14:23 Robert Watson said the following:
>> I've been keeping a vague eye out for this over the last few years, and haven't
>> spotted many problems in production machines I've inspected.  You can use the
>> umastat tool in the tools tree to look at the distribution of memory over
>> buckets (etc) in UMA manually.  It would be nice if it had some automated
>> statistics on fragmentation however.  Short-lived fragmentation is likely, and
>> isn't an issue, so what you want is a tool that monitors over time and reports
>> on longer-lived fragmentation.
>> 
>> The main fragmentation issue we've had in the past has been due to mbuf+cluster
>> caching, which prevented mbufs from being freed usefully in some cases.  Jeff's
>> ongoing work on variable-sized mbufs would entirely eliminate that problem...
> 
> just in case, this thread is not about fragmentation, it's about per-cpu
> buckets, number of items in them and size of the items.

Those issues are closely related, and in particular, wanted to point Andre at umastat since he's probably not aware of it.. :-)

Robert