Re: -mmX 4G patches feedback [numbers: how much performance impact]

[Andrea Arcangeli <andrea@suse.de>]

On Wed, Apr 07, 2004 at 03:58:25PM -0700, Martin J. Bligh wrote:
> so .... such microbenchmarks seems pointless. I'm not against 4/4G at all,
> I think it solves a real problem ... I just think latency numbers are a 

I agree as well it solves a real problem (i.e. 4G userspace), though the
userbase that needs it is extremely limited and they're sure ok to run
slower than to change their application to use shmfs (a special 4:4
kernel may be ok, just like a special 2.5:1.5 may be ok, just like
3.5:0.5 was ok for similar reasons too), but the mass market doesn't
need 4:4 and it will never need it, so it's bad to have the masses pay
for this relevant worthless runtime overhead in various common
workloads.

Of course above I'm talking about 2.6-aa or 2.6-mjb. Clearly with
kernels including rmap like 2.6 mainline or 2.6-mm or 2.6-mc or the
2.4-rmap patches you need 4:4 everywhere, even on a 4/8G box to avoid
running out of normal zone in some fairly common and important workload.