Date: Mon, 24 Mar 2003 18:12:55 -0800 From: Wes Peters <wes@softweyr.com> To: David Schultz <das@FreeBSD.ORG> Cc: freebsd-arch@FreeBSD.ORG Subject: Re: Patch to protect process from pageout killing Message-ID: <200303241812.55290.wes@softweyr.com> In-Reply-To: <20030325012303.GA4406@HAL9000.homeunix.com> References: <200303240823.48262.wes@softweyr.com> <20030325012303.GA4406@HAL9000.homeunix.com>
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On Monday 24 March 2003 17:23, David Schultz wrote:
> Thus spake Wes Peters <wes@softweyr.com>:
> > As promised, here's the patch to protect a process from being
> > killed when pageout is in memory shortage. This allows a process
> > to specify that it is important enough to be skipped when pageout
> > is looking for the largest process to kill.
> >
> > My needs are simple. We make a box that is a web proxy and runs
> > from a memory disk, using flash for permanent storage. The flash
> > is mounted only when a configuration write is needed, the box runs
> > from the memory disk. We've experienced a problem at certain
> > customer sites where bind will consume a lot (~30 MB) of ram and
> > then pageout will kill the largest process, which is usually either
> > named or squid. This pretty much kills the box. We'd much rather
> > have pageout kill off some of the squid worker processes, we can
> > recover from that.
>
> Very nice. Inheritance of this attribute seems to be a
> contentious issue. Making inheritance tunable might be a good
> idea. You wouldn't be able to piggyback on rlimit, though.
Actually inheritance was unintentional, I'm waiting for feedback on what
I should've done to make it not inherited. Any help you can offer will
be appreciated.
> There's a significant userland component of this as well, although
> that's probably a job for another day. It basically consists of
> making it possible to specify that certain standard system daemons
> should have this attribute.
Yup.
> > + (p->p_flag & P_PROTECTED) ||
> > ((p->p_pid < 48) && (vm_swap_size != 0))) {
> > PROC_UNLOCK(p);
> > continue;
>
> The pid < 48 magic can probably go away, while you're at it.
I'd be happy to -- that 48 makes me nervous -- if a couple more Really
Smart(tm) guys say it's OK. ;^)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters wes@softweyr.com
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