Date: Wed, 16 Jul 2003 09:51:46 +0000 From: Bosko Milekic <bmilekic@technokratis.com> To: Scot Loach <sloach@sandvine.com> Cc: "'freebsd-net@freebsd.org'" <freebsd-net@freebsd.org> Subject: Re: Kernel tuning for large maxsockets Message-ID: <20030716095146.GB13330@technokratis.com> In-Reply-To: <FE045D4D9F7AED4CBFF1B3B813C8533701AE8534@mail.sandvine.com> References: <FE045D4D9F7AED4CBFF1B3B813C8533701AE8534@mail.sandvine.com>
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On Tue, Jul 15, 2003 at 05:22:55PM -0400, Scot Loach wrote: > Currently, whenever maxsockets is increased, this causes kernel memory to be > preallocated for each type of pcb (tcp, udp, raw, divert). The number of > pcbs preallocated for each of these is always the same as maxsockets. > > This is probably a waste of memory for raw sockets and divert sockets, since > they would not normally be used in large numbers. A large server could > save kvm by reducing the number of divert and raw pcbs preallocated. For > example, on a machine configured for 200,000 maxsockets we would save 75MB > of kvm out of a total of 262MB that would have been preallocated. This kvm > savings can be used to increase maxsockets even more. What version of FreeBSD are you talking about here? In -current, the pcbs come off of zones which are capped at a maximum w.r.t. maxsockets. The kva space comes out of kmem_map and the objects are kept cached in their respective zones. One thing to note is that the zones are setup with UMA_ZONE_NOFREE, so the pages wired down for pcb use are probably never unwired. I don't know why, exactly, UMA_ZONE_NOFREE is required for all of the pcb zones in the netinet code. > Is there any reason I should not modify the kernel code to only let a small, > fixed number of raw and divert pcbs be preallocated instead of having them > scale with maxsockets? > > Next, does this seem like a generally useful thing that could be rolled back > into the source tree? I could make this a kernel option or a tunable sysctl > variable. > > thanks > > Scot Loach -- Bosko Milekic * bmilekic@technokratis.com * bmilekic@FreeBSD.org TECHNOkRATIS Consulting Services * http://www.technokratis.com/
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