mmap on Linux

NSD
1

Hello,

This question is mainly directed to the developers. I am building an RPM
package of NSD 2.3.7 for use on CentOS 4.5. I notice that one of the
options available during the configure phase is "--enable-mmap". The
release notes briefly mention it as being useful on Solaris, but don't
talk about any other OS. Since it is not enabled by default, I'd like to
ask whether there is any benefit to be had on enabling it on CentOS.

2

Anand Buddhdev wrote:

This question is mainly directed to the developers. I am building an RPM
package of NSD 2.3.7 for use on CentOS 4.5. I notice that one of the
options available during the configure phase is "--enable-mmap". The
release notes briefly mention it as being useful on Solaris, but don't
talk about any other OS. Since it is not enabled by default, I'd like to
ask whether there is any benefit to be had on enabling it on CentOS.

It has to do with memory overcommit. A usefull reference is:
http://developers.sun.com/solaris/articles/subprocess/subprocess.html#overcom

To answer your question, you don't need it on Linux.

Mark

- --
Mark Santcroos
NLnet Labs
http://www.nlnetlabs.nl/

3

Mark Santcroos wrote:

Anand Buddhdev wrote:

This question is mainly directed to the developers. I am building an RPM
package of NSD 2.3.7 for use on CentOS 4.5. I notice that one of the
options available during the configure phase is "--enable-mmap". The
release notes briefly mention it as being useful on Solaris, but don't
talk about any other OS. Since it is not enabled by default, I'd like to
ask whether there is any benefit to be had on enabling it on CentOS.

It has to do with memory overcommit. A usefull reference is:
http://developers.sun.com/solaris/articles/subprocess/subprocess.html#overcom

To answer your question, you don't need it on Linux.

Some further info:

This feature is not present in NSD v3.
To make you even sleep better tonight, it is also not part of the entire
history of NSD v2 :slight_smile:
The last version that had this was NSD v1.

So what you have stumbled upon is leftover configure magic that should
have been removed ages ago (and will be gone in the next release).

Mark

- --
Mark Santcroos
NLnet Labs
http://www.nlnetlabs.nl/

4

Why not grab the SRPM from fedora?

Paul

5

Paul Wouters writes:

Anand Buddhdev wrote:
> This question is mainly directed to the developers. I am building an RPM
> package of NSD 2.3.7 for use on CentOS 4.5. I notice that one of the

Why not grab the SRPM from fedora?

That's what I have actually done, and the spec file of the SRPM passes '--enable-mmap' to configure. That's the reason I was asking about it. Now that Marc has provided the answer I was looking for, I can edit the SPEC file, incorporating some other minor changes to build the RPM according to my taste.