On Wed, Jul 14, 2004 at 08:33:51AM -0400, Steven M. Bellovin wrote:
> In message <20040714033948.GB13570@che.ojctech.com>, David Young writes:
> >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.
> >
> You and Andrew make good points about special cases.  I should amend my 
> suggestion: does MFS make sense for /tmp on ordinary machines?

Something like it, yes; I don't want to waste a disk partition for /tmp.

	-is
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