Date: Thu, 1 Jun 2006 15:01:11 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: Jonathan Noack <noackjr@alumni.rice.edu> Cc: freebsd-current@FreeBSD.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: md /tmp and async mounts Message-ID: <20060601120111.GA5507@gothmog.pc> In-Reply-To: <447E7540.8070904@alumni.rice.edu> References: <20060522211223.GA3621@xor.obsecurity.org> <20060522231437.GC1446@odin.ac.hmc.edu> <20060523133037.GA2908@gothmog.pc> <20060523143013.GA11472@ci0.org> <20060523194106.GA46634@xor.obsecurity.org> <20060524203645.GB13500@gothmog.pc> <20060524203747.GA88742@xor.obsecurity.org> <20060524204617.GA13701@gothmog.pc> <20060601002024.GA1453@gothmog.pc> <447E7540.8070904@alumni.rice.edu>
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On 2006-06-01 01:04, Jonathan Noack <noackjr@alumni.rice.edu> wrote: > On 05/31/06 20:20, Giorgos Keramidas wrote: > > The following diff should be sufficient for enabling -o async for > > the MFS /tmp and MFS /var filesystems we support in our current > > rc.d stuff: > > > > %%% > > Index: share/man/man5/rc.conf.5 > > =================================================================== > > --- share/man/man5/rc.conf.5 (revision 99) > > +++ share/man/man5/rc.conf.5 (revision 101) > > @@ -24,7 +24,7 @@ > > .\" > > .\" $FreeBSD: src/share/man/man5/rc.conf.5,v 1.298 2006/05/30 16:20:48 matteo Exp $ > > .\" > > -.Dd May 29, 2006 > > +.Dd Jun 1, 2006 > > .Dt RC.CONF 5 > > .Os > > .Sh NAME > > @@ -241,12 +241,13 @@ > > .Pa /tmp > > is created. > > The default is > > -.Dq Li "-S -M" , > > +.Dq Li "-S -M -o async" , > > which inhibits the use of softupdates on > > .Pa /tmp > > to waste as little space as possible > > -and creates a pure memory backed disk, which will never be swapped out, > > -for maximum performance and system stability at low memory conditions. > > +and creates a pure memory-backed disk, which uses asynchronous I/O > > +and will never be swapped out, for maximum performance and system > > +stability at low memory conditions. > > Given recent posts about panics with malloc-backed mds under > low-memory conditions (see the "kmem leak in tmpmfs?" thread on > stable@), I'm not sure keeping '-M' as the default for tmpmfs > and varmfs is advisable. Here is the rather ominous note on > using malloc-backed mds in mdconfig(8): "Storage for this type > of memory disk is allocated with malloc(9). This limits the > size to the malloc bucket limit in the kernel. If the -o > reserve option is not set, creating and filling a large > malloc-backed memory disk is a very easy way to panic a > system." Note that the -M option has *been* already the default for ages. I am not suggestting to change these options in this patch.
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