Date: Sat, 18 Sep 2010 12:30:41 +0100 From: "Robert N. M. Watson" <rwatson@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: zfs + uma Message-ID: <52AE93F3-D15F-40C9-A9CA-07F30C803B81@freebsd.org> In-Reply-To: <4C94A22F.1070608@freebsd.org> References: <4C93236B.4050906@freebsd.org> <4C935F56.4030903@freebsd.org> <alpine.BSF.2.00.1009181221560.86826@fledge.watson.org> <4C94A22F.1070608@freebsd.org>
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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=
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