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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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final followup I think.

the sigstop I see after every fork from strace is

PID --- SIGSTOP (Stopped (signal)) @ 0 (0) ---

don't know what the @ 0 (0) means

On Thu, 2003-03-13 at 21:03, Shaya Potter wrote:
> 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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