Subject: Re: fork/sh/hello microbenchmark performance in chroot
From: Shaya Potter <spotter@cs.columbia.edu>
To: linux-kernel@vger.kernel.org
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Date: 13 Mar 2003 21:03:53 -0500
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and a little more followup.  The chroot is basically a machine's fs's
mounted over nfs over an ipsec tunnel

/chroot/"filesystems"

when I run it /chroot/tmp/benchmark/forksh, I get .2s

but when I chroot into the /chroot tree and run /tmp/benchmark/forksh I
get 1s.

If I make the chroot tree just composed of mount -o bind'd fs from the
host machine, I don't see the slow down.

so to recap

plain linux, local filesystems - it's fine
plain linux, nfs over ipsec filesystems - it's fine
chrooted linux, local filesystems - it's fine
chrooted linux, nfs over ipsec filesystems - it's very slow.

thanks,

shaya

On Thu, 2003-03-13 at 20:54, Shaya Potter wrote:
> in a followup, the only thing I can tell difference b/w the 2 runs
> (under strace and inside and outside of the chroot) is that within the
> chroot, after every fork() I see a SIGSTOP on the child.
> 
> anyone have any idea why this is happening?
> 
> On Thu, 2003-03-13 at 20:43, Shaya Potter wrote:
> > I'm trying to play with our a homebrew version of lmbench's fork
> > benchmark which exec's sh to run a "hello world" program.  On normal
> > 2.4.18 (UP 933mhz p3) it runs in about .2s  However, within a chrooted
> > environment I'm looking at 1s.
> > 
> > Anyone knows why this runs significantly slower within a chroot?
> > 
> > thanks,
> > 
> > shaya
> > 
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