Date: Sat, 07 Sep 2013 13:56:02 -0600 From: Ian Lepore <ian@FreeBSD.org> To: hiren panchasara <hiren.panchasara@gmail.com> Cc: freebsd-net@FreeBSD.org, "freebsd-mips@freebsd.org" <freebsd-mips@FreeBSD.org>, Warner Losh <imp@bsdimp.com> Subject: Re: mbuf autotuning effect Message-ID: <1378583762.1111.512.camel@revolution.hippie.lan> In-Reply-To: <CALCpEUHh9o-scuoj_p-MGMZKn2d_Bbhtf8djV8MsLeOF8%2BKG9A@mail.gmail.com> 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>
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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. 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. -- Ian
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