Date: Fri, 8 Mar 2013 12:09:56 -0500 From: Garrett Wollman <wollman@bimajority.org> To: Andre Oppermann <andre@freebsd.org> Cc: jfv@freebsd.org, freebsd-net@freebsd.org, Garrett Wollman <wollman@freebsd.org> Subject: Re: Limits on jumbo mbuf cluster allocation Message-ID: <20794.7012.265887.99878@hergotha.csail.mit.edu> In-Reply-To: <51399926.6020201@freebsd.org> References: <20793.36593.774795.720959@hergotha.csail.mit.edu> <51399926.6020201@freebsd.org>
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<<On Fri, 08 Mar 2013 08:54:14 +0100, Andre Oppermann <andre@freebsd.org> said: > [stuff I wrote deleted] > You have an amd64 kernel running HEAD or 9.x? Yes, these are 9.1 with some patches to reduce mutex contention on the NFS server's replay "cache". > Jumbo pages come directly from the kernel_map which on amd64 is 512GB. > So KVA shouldn't be a problem. Your problem indeed appears to come > physical memory fragmentation in pmap. I hadn't realized that they were physically contiguous, but that makes perfect sense. > pages. Also since you're doing NFS serving almost all memory will be > in use for file caching. I actually had the ZFS ARC tuned down to 64 GB (out of 96 GB physmem) when I experienced this, but there are plenty of data structures in the kernel that aren't subject to this limit and I could easily imagine them checkerboarding physical memory to the point where no contiguous three-page allocations were possible. -GAWollman
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