cvs commit: src/sys/kern subr_param.c sys_pipe.c src/sys/sys pipe.h

[Bosko Milekic]

On Thu, Jul 10, 2003 at 02:19:21PM -0500, Alan L. Cox wrote:
[...]
> > That would alleviate the KVA pressure, since the mapping would be
> > very temporary and you could even get away with just a single
> > page.  However, it would still tie up the associated physical
> > memory until the pipe is read, which may not be soon at all.  Is
> > there a reason for the memory to be wired, other than that the
> > data is easier to track down while the sending process' PTEs are
> > still there?  I would expect that you could instead just look up
> > the appropriate vm_object and lazily fault in the appropriate pages
> > on the receiver's side, modulo a few details such as segfault handling.
> > But perhaps I'm missing something...
> 
> It's a matter of priorities.  With the growth trend in physical memory
> sizes (and PAE), I see more problems due to KVA pressure than
> unnecessarily wired memory.  A recent, and fairly visible example, was
> the vnode autosizing problems that had to be fixed prior to 5.1-RELEASE.

  With the recent bug reporting regarding kmem_map being too small
  coming in, I'd have to say that I agree with that assertion.  Address
  space has become more expensive than memory, at least on ia32, and
  it's gotten to the point where we need to re-evaluate some of our
  autosizing and max size constants (for example, see VM_KMEM_SIZE_MAX).

> Regards,
> Alan

Regards,
-- 
Bosko Milekic  *  bmilekic at technokratis.com  *  bmilekic at FreeBSD.org
TECHNOkRATIS Consulting Services  *  http://www.technokratis.com/