Date: Mon, 24 Mar 2003 17:23:03 -0800 From: David Schultz <das@FreeBSD.ORG> To: Wes Peters <wes@softweyr.com> Cc: freebsd-arch@FreeBSD.ORG Subject: Re: Patch to protect process from pageout killing Message-ID: <20030325012303.GA4406@HAL9000.homeunix.com> In-Reply-To: <200303240823.48262.wes@softweyr.com> References: <200303240823.48262.wes@softweyr.com>
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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.
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.
> + (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.
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