[rds-devel] FW: RDS -- how to detect peer is gone ?

Greg Lindahl lindahl at pbm.com
Wed Mar 31 15:08:22 PDT 2010


On Wed, Mar 31, 2010 at 02:40:19PM -0700, Andy Grover wrote:
> Tang, Changqing wrote:
> > Why not ? even IB verbs support both 32bit and 64bit apps.
> 
> We support 32bit apps on a 32bit kernel and 64bit apps on a 64bit
> kernel. You are talking about some kind of 32bit userspace on a 64bit
> kernel. Nobody does that.

It is very common for 64-bit kernels to have a userspace installed that
allows both 32-bit and 64-bit apps.

The only distro which didn't initially do this on x86-64 was Debian,
and they changed their mind soon after.

Why would you run 32-bit apps on a 64-bit kernel? Smaller pointers can
sometimes significantly improve cache behavior and thus performance on
apps which are very pointer-heavy.  One example that gets ~ a 2X
performance improvement in 32-bits is the PathScale compiler.

Some people even run a pure 32-bit userspace over a 64-bit kernel,
because memory management of 'large' RAM is much better that way,
but they don't want to change their userland.

-- greg






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