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From: "Robert N. M. Watson" <rwatson@FreeBSD.org>
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To: Alan Cox <alc@rice.edu>
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	Ivan Voras <ivoras@freebsd.org>
Subject: Re: Analyzing wired memory?
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On 8 Feb 2011, at 10:37, Alan Cox wrote:

>> John and I have occasionally talked about making procstat -v work on =
the kernel; conceivably it could also export a wired page count for =
mappings where it makes sense.  Ideally procstat would drill in a bit =
and allow you to see things at least at the granularty of "this page =
range was allocated to UMA".
>=20
> I would certainly have found this useful on a few occasions, and would =
gladly help out with implementing it.  For example, it would help us in =
understanding the kmem_map fragmentation caused by ZFS.  That said, I'm =
not sure how you will represent the case where UMA allocates physical =
memory directly and uses the direct map to access it.

I agree -- in some sense, my proposal is related to, but somewhat =
orthogonal to, the problem Ivan is running into.

We could also have a more detailed but UMA-specific inspection tool; I =
have a uma dumping tool in src/tools somewhere that dumps zone =
information, buckets, etc, for UMA types. I've used this in the past to =
explore mbuf alloc/free behaviour, multi-CPU imbalances in allocation, =
over-caching, etc. It may be time to revisit that, decide how to make it =
a bit more user/developer-friendly, and make it a formally supported =
tool as part of vmstat (which involves adding some new sysctls as well).

Robert