Date: Tue, 6 Feb 2007 01:54:36 -0600 (CST) From: Mike Silbersack <silby@silby.com> To: Randall Stewart <rrs@cisco.com> Cc: Luigi Rizzo <rizzo@icir.org>, freebsd-net <freebsd-net@freebsd.org> Subject: Re: mbuf patch with sysctl suggestions too Message-ID: <20070206014950.S25997@odysseus.silby.com> In-Reply-To: <45B7631A.3070001@cisco.com> References: <45B679F3.3080407@cisco.com> <20070124051050.A56064@xorpc.icir.org> <45B7631A.3070001@cisco.com>
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On Wed, 24 Jan 2007, Randall Stewart wrote: > Well.. no I believe someone (was in Lin) mentioned that > you can get a live-lock if you allow a reduction.. and > thus the mbuf clusters were NOT allowed to be reduced.. I messed around with this a bit when changing the limit on net.inet.tcp.maxtcptw. It looked to me as if lowering the limit on a zone, even one that has UMA_ZONE_NOFREE, worked as expected. (As expected in the UMA_ZONE_NOFREE case was that the zone could not shrink below the maximum that was ever allocated in it.) I can see how problems could result if someone starts changing that setting while the system is in some sort of mbuf exhaustion state, but I think that the benefit of being able to tune it most of the time far outweighs the disadvantage of things going wrong in a few cases. Granted, I haven't even looked at your patch, so I could be missing something subtle. :) Mike "Silby" Silbersack
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