[ale] chroot and /proc?

[Jeff Lightner]

I guess I should have mentioned the OP on the BIND list specifically
stated that using "-n 4" still only resulted in BIND finding 1 CPU.

 

Later discussion on the BIND list (after I'd posted here) indicates:

After quick look into bind and glibc code /proc has to be mounted.

named calls sysconf(3) function and internal glibc implementation looks
like this:

 

__get_nprocs () {

..

  FILE *fp = fopen ("/proc/stat", "rc");

  if (fp != NULL) {

    ..

  } else {

    fp = fopen ("/proc/cpuinfo", "rc");

    if (fp != NULL) {

      ..

    }

    ..

  }

 

  return 1;

}

 

So if you don't have /proc mounted in chroot glibc is not able to get
number of CPUs and returns 1. When you don't need detect correct number
of CPUs (always use one CPU) then you don't have to mount /proc

 

The poster was from RedHat and in a later post indicated he was going to
work on a patch to determine number of CPUs BEFORE BIND starts the
chroot environment as suggested in response to the above.

 

That seems to sum it up nicely for me.

 

________________________________

From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of
Jason Fritcher
Sent: Tuesday, April 01, 2008 2:20 PM
To: ale at ale.org
Subject: Re: [ale] chroot and /proc?

 

 

On Apr 1, 2008, at 12:09 PM, Jeff Lightner wrote:

	Alternatively I'm wondering if there isn't a better way to let
the chroot environment BIND know that there are 4 CPUs?

 

Sure, there is a command-line option to tell it how many CPUs there
are...

 

       -n #cpus

          Create #cpus worker threads to take advantage of multiple
CPUs. If

          not specified, named will try to determine the number of CPUs

          present and create one thread per CPU. If it is unable to
determine

          the number of CPUs, a single worker thread will be created.

 

-- 

Jason Fritcher

jkf at wolfnet.org
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