Subject: Re: mfs woes
To: None <tech-kern@NetBSD.org>
From: David Young <email@example.com>
Date: 07/13/2004 22:39:48
On Tue, Jul 13, 2004 at 11:17:20PM -0400, Steven M. Bellovin wrote:
> In message <20040713230112.A426@noc.untraceable.net>, Andrew Brown writes:
> >On Tue, Jul 13, 2004 at 05:18:31PM -0500, David Young wrote:
> >>I am told that blocks in the memory filesystem (mfs) can end up in the
> >>buffer cache: this double-whammy on memory can lead to memory exhaustion.
> >yes, 'cause it's a "file system".
> >>The problem is compounded (I do not understand how or why) when multiple
> >>mfs are in use.
> >>Is there any bug-fix or work-around for the memory-inefficiency/exhaustion
> >>issue? Can somebody outline what a fix would look like?
> >write a real swap-based file system? mfs also comes with a ~2.9
> >gigabyte limit (on i386, at least). when using USE_TOPDOWN_VM. when
> >you're not, it comes with a ~1.8 gigabyte limit. regardless of how
> >much ram or swap you have.
> Given the new buffer cache architecture, I've been wondering if mfs
> even makes sense these days. Perhaps a disk partition mounted with
> async would provide comparable performance? I don't know; I haven't
> tried it. But I'm getting ready to bring up a new machine; I might
> reserve a partition and see what happens.
I think that an in-memory filesystem makes the most sense for my
applicatoin: I am using either a CompactFlash card or a CD-ROM as the
"hard drive." I do not want to keep volatile information on the former;
I cannot keep it on the latter.
David Young OJC Technologies
firstname.lastname@example.org Urbana, IL * (217) 278-3933