Subject: Re: mfs woes
To: Andrew Brown <email@example.com>
From: Steven M. Bellovin <firstname.lastname@example.org>
Date: 07/13/2004 23:17:20
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.
--Steve Bellovin, http://www.research.att.com/~smb