Re: mbuf tuning
From: Igor Sysoev (is_at_rambler-co.ru)
Date: 01/19/04
- Previous message: Willem Jan Withagen: "Old SUN NFS performance papers."
- In reply to: CHOI Junho: "Re: mbuf tuning"
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Date: Tue, 20 Jan 2004 00:19:54 +0300 (MSK) To: CHOI Junho <cjh@kr.FreeBSD.org>
On Mon, 19 Jan 2004, CHOI Junho wrote:
> From: Mike Silbersack <silby@silby.com>
> Subject: Re: mbuf tuning
> Date: Mon, 19 Jan 2004 01:12:08 -0600 (CST)
>
> > There are no good guidelines other than "don't set it too high." Andre
> > and I have talked about some ideas on how to make mbuf usage more dynamic,
> > I think that he has something in the works. But at present, once you hit
> > the wall, that's it.
> >
> > One way to reduce mbuf cluster usage is to use sendfile where possible.
> > Data sent via sendfile does not use mbuf clusters, and is more memory
> > efficient. If you run 5.2 or above, it's *much* more memory efficient,
> > due to change Alan Cox recently made. Apache 2 will use sendfile by
> > default, so if you're running apache 1, that may be one reason for an
> > upgrade.
>
> I am using custom version of thttpd. It allocates mmap() first(builtin
> method of thttpd), and it try to use sendfile() if mmap() fails(out of
> mmap memory). It really works good in normal status but the problem is
> that sendfile buffer is also easy to flood. I need more sendfile
> buffers but I don't know how to increase sendfile buffers either(I
> think it's hidden sysctl but it was more difficult to tune than
> nmbclusters). With higher traffic, thttpd sometimes stuck at "sfbufa"
> status when I run top(I guess it's "sendfile buffer allocation"
> status).
In 4.x you have to rebuild the kernel with
options NSFBUFS=16384
It equals to (512 + maxusers * 16) by default.
By the way, why do you want to use the big net.inet.tcp.sendspace and
net.inet.tcp.recvspace ? It makes a sense for Apache but thttpd can easy
work with the small buffers, say, 16K or even 8K.
> > > Increasing kern.ipc.nmbclusters caused frequent kernel panic
> > > under 4.7/4.8/4.9. How can I set more nmbclusters value with 64K tcp
> > > buffers? Or is any dependency for mbufclusters value? (e.g. RAM size,
> > > kern.maxusers value or etc)
> > >
> > > p.s. RAM is 2G, Xeon 2.0G x 1 or 2 machines.
> >
> > You probably need to bump up KVA_PAGES to fit in all the extra mbuf
> > clusters you're allocating.
>
> Can you tell me in more detail?
>From LINT:
--- # # Change the size of the kernel virtual address space. Due to # constraints in loader(8) on i386, this must be a multiple of 4. # 256 = 1 GB of kernel address space. Increasing this also causes # a reduction of the address space in user processes. 512 splits # the 4GB cpu address space in half (2GB user, 2GB kernel). # options KVA_PAGES=260 --- Default KVA_PAGES are 256. Igor Sysoev http://sysoev.ru/en/ _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscribe@freebsd.org"
- Previous message: Willem Jan Withagen: "Old SUN NFS performance papers."
- In reply to: CHOI Junho: "Re: mbuf tuning"
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