mbuf patch with sysctl suggestions too

[Luigi Rizzo]

On Wed, Jan 24, 2007 at 08:46:02AM -0500, Randall Stewart wrote:
> Luigi Rizzo wrote:
> > On Tue, Jan 23, 2007 at 04:11:15PM -0500, Randall Stewart wrote:
> >> Hi all:
> >>
> >> Here is iteration 2 of the mbuf patch with limits I
> >> proposed.
> >>
> >> Also note the changes for sysctl stuff that Lugi suggested.
> >> Please let me know what you think :-)
> > 
> > ...
> >> +	newnmbjclusters = nmbjumbop;
> >> +	error = sysctl_int_checked(oidp, &newnmbjclusters, nmbjumbop, 
> >> +           SYSCTL_NO_LIMIT, req);
> > 
> > A few things here:
> > - i don't see much of a point in defining SYSCTL_NO_LIMIT;
> >   UINT32_MAX would do perfectly there, and i think it is easier
> >   to understand than SYSCTL_NO_LIMIT (which looks like a flag).
> > 
> 
> ok
> > - here and in other places you do not allow decresaing the value
> >   (by putting min = nmbjumbop etc.), and i am not sure why.
> >   I understand a reasonable lower bound, but i guess the worst
> >   that can happen, when you reduce the limit to something above
> >   the current allocation, is that nothing is allocated until
> >   you go again below the limit, right ?
> 
> Well.. no I believe someone (was in Lin) mentioned that
> you can get a live-lock if you allow a reduction.. and
> thus the mbuf clusters were NOT allowed to be reduced..

maybe... but then this is definitely worth putting a note
explaining why.

	cheers
	luigi