Date: Sat, 7 Sep 2013 17:25:15 -0700 From: hiren panchasara <hiren.panchasara@gmail.com> To: Ian Lepore <ian@freebsd.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org>, Warner Losh <imp@bsdimp.com> Subject: Re: mbuf autotuning effect Message-ID: <CALCpEUHuQLUnx=Jh0_p3wC%2BU=7OxfqfzE7gLDJ2cC4bDnNVCyA@mail.gmail.com> In-Reply-To: <1378583762.1111.512.camel@revolution.hippie.lan> References: <CALCpEUHoAS2RRyO7JVOeSKWKiss9vZmN%2BxA1BDpwHDpkEYcjEA@mail.gmail.com> <CAJ-VmomAjsU%2Bnc=4AEdSn5gDhspc2YVrDtPophJvmee1kSTYog@mail.gmail.com> <9CBFAD35-D651-4E28-BEBB-DC3717F38567@bsdimp.com> <CALCpEUHh9o-scuoj_p-MGMZKn2d_Bbhtf8djV8MsLeOF8%2BKG9A@mail.gmail.com> <1378583762.1111.512.camel@revolution.hippie.lan>
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On Sat, Sep 7, 2013 at 12:56 PM, Ian Lepore <ian@freebsd.org> wrote: > On Sat, 2013-09-07 at 12:21 -0700, hiren panchasara wrote: > > On Sep 6, 2013 8:26 PM, "Warner Losh" <imp@bsdimp.com> wrote: > > > > > > > > > On Sep 6, 2013, at 7:11 PM, Adrian Chadd wrote: > > > > > > > Yeah, why is VM_KMEM_SIZE only 12mbyte for MIPS? That's a little > > low > > for a > > > > platform that has a direct map that's slightly larger than 12mb :) > > > > > > > > Warner? Juli? > > > > > > All architectures have it at 12MB, except sparc64 where it is 16MB. > > This > > can be changed with the options VM_KMEM_SIZE=xxxxx in the config file. > > > > Right. Does that mean for any platform, if we do not have nmbclusters > > pre-set in kmeminit() than we will always have pretty low value of > > vm_kmem_size. And because of that, if maxmbufmem is not pre-set (via > > loader.conf) inside tunable_mbinit() , we will have very low value for > > maxmbufmem too. > > > > I hope (partially believe) that my understanding is not entirely > > correct. > > Because if its correct, we arw depending on loader.conf instead of > > actually > > auto tuning. > > > I think the part of this that strikes me as strange is calling 20% of > physical memory used for network buffers a "very low value". It seems > outrageously high to me. I'd be pissed if that much memory got wasted > on network buffers on one of our $work platforms with so little memory. > Interesting. So here how it looks on my laptop running amd64 GENERIC looks like: (without any special loader.conf settings) flymockour-l7% uname -a FreeBSD flymockour-l7.corp.yahoo.com 10.0-CURRENT FreeBSD 10.0-CURRENT #1 r253512M: Sat Jul 20 23:00:51 PDT 2013 hirenp@flymockour-l7.corp.yahoo.com:/usr/obj/usr/home/hirenp/head/sys/GENERIC amd64 flymockour-l7% sysctl -a | grep hw| grep mem hw.physmem: 8496877568 hw.usermem: 3538432000 hw.realmem: 9093251072 flymockour-l7% sysctl kern.ipc.maxmbufmem kern.ipc.maxmbufmem: 4132540416 flymockour-l7% sysctl -a | grep vm.kmem_ vm.kmem_size: 8265080832 vm.kmem_size_min: 0 vm.kmem_size_max: 329853485875 vm.kmem_size_scale: 1 vm.kmem_map_size: 1380515840 vm.kmem_map_free: 5796265984 VM_KMEM_SIZE_SCALE is 1 for amd64 while 3 for mips. Which might be one reason. > So the fact that you think it's crazy-low and I think it's crazy-high > may be a sign that it's auto-tuned to a reasonable compromise, and in > both our cases the right fix would be to use the available knobs to tune > things for our particular uses. > I am pretty ignorant on what the value _should_ be. I will try to find out more. cheers, Hiren
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