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From: "Robert N. M. Watson" <rwatson@freebsd.org>
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To: Andriy Gapon <avg@freebsd.org>
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Subject: Re: zfs + uma
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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.
>>=20
>> 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...
>=20
> 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=