Patch to protect process from pageout killing

[Wes Peters]

On Wednesday 26 March 2003 09:13, John Baldwin wrote:
> On 26-Mar-2003 Wes Peters wrote:
> > On Tuesday 25 March 2003 08:34, John Baldwin wrote:
> >> On 25-Mar-2003 Wes Peters wrote:
> >> > On Monday 24 March 2003 08:36, Poul-Henning Kamp wrote:
> >> >> Also, doesn't this result in the flag being inerited with
> >> >> fork() and thereby negating the effect you are seeking for
> >> >> squid ?
> >> >
> >> > I looked through all the places in kern_fork.c where p2->p_flag
> >> > gets set and didn't see anything that looked like it would
> >> > inherit P_PROTECTED from p1->p_flag.  Did I miss something?  I'm
> >> > obviously a bit of a neophyte in this part of the kernel.
> >>
> >> rlimit's are inherited.  However, due to a "feature" bug in your
> >> patch, the P_PROTECTED flag doesn't get turned on when the rlimit
> >> is inherited in fork1().
> >
> > feature bug?  If you mean the fact that the setting for P_PROTECTED
> > isn't stored in the rlimit, that was intentional.  rlimits are
> > inherited and I specifically didn't want that behavior, similar to
> > p_cpulimit.  I still agree resource limits are not an ideal
> > interface to use for this, I'll look further.
>
> I mean that you should be setting P_PROTECTED in fork() based on the
> inherited rlimit's since otherwise the value of the rlimit is out of
> sync with the P_PROTECTED flag.  Hence a bug.  However, since non-
> inheritance is the desired behavior, it is also a feature, hence
> "feature" bug.

Ah, actually it would be best to explicitly clear the RLIMIT_PROTECT in 
the rlimit, except the RLIMIT_PROTECT isn't stored in the rlimit.  Eww, 
that was not good.  Problem is, there isn't a generic syscall for 
munging proc items.  As I said, it was a less-than-optimal syscall to 
abuse, I'll go back to pondering madvise(2) or mprotect(2) which almost 
sort of make sense.

-- 
         "Where am I, and what am I doing in this handbasket?"

Wes Peters                                              wes at softweyr.com