using mfs of size > 64Mb and system stability

[Barath S]

Initially, I didn't go for swap based fs as I felt
that  the memory occupied will be from the swap area.
As you are saying that the allocation will be from
buffer/cache, I will test swap-mfs.

Updates on malloc-mfs:

System didn't crash when creating malloc based fs with
"-o reserve" option for a size of 128Mb.  But, when
tried creating two mfs(s) each with sizes of 24Mb and
1Mb, the system rebooted itself. I tried this in a
system with 1G memory. Another observation is that
even  with this system w/o "-o reserve", the system
hangs immediately with mfs-size > 64Mb.


Thanks and regards 
 --- Scott Long <scottl at freebsd.org> wrote:   
> Using the swap option really is the preferred
> method.  The available
> kernel malloc pool is limited and is scaled on the
> amount of system
> RAM that you have; on my 256MB laptop, it's
> reporting only 85MB
> available for kernel malloc.  So this would explain
> why trying to
> malloc 128MB for md could fail =-).
> 
> With the swap option, pages are allocated from the
> buffer/cache and
> held there.  They are only swapped to disk when the
> system is under
> memory pressure, otherwise they stay in RAM.
> 
> Scott
> 
> Barath S wrote:
> > Thank you Arne. 
> > I didn't try with 'swap' option as my requirement
> is
> > to have the files in memory. I will test with 5.3
> and
> > see it that works.
> > regards
> > --- Arne Wörner <arne_woerner at yahoo.com> wrote:   
> > 
> >>--- Barath S <barath_yes at yahoo.com.sg> wrote:
> >>
> >>>My intention is create a file system in memory of
> >>
> >>size
> >>
> >>>>128Mb and use that for my application. But, I
> >>>
> >>>couldn't do that as my system hangs whenever I
> >>
> >>create
> >>
> >>>a mfs of size > 64Mb. I did the following...
> >>>
> >>>a) Configured memory file system of size 128Mb
> >>
> >>using
> >>
> >>>'mdmfs' command with 'malloc' option. When I
> tried
> >>
> >>to
> >>
> >>>copy files to this mfs, m/c hanged after copying
> >>
> >>some
> >>
> >>>files. 
> >>>b) Then I rebooted by m/c and configured memory
> >>
> >>file
> >>
> >>>system of size 64Mb and this time the copying
> >>>operation was successful
> >>>c) I observed that the system hanged whenever I
> >>>configure a mfs of size > 64Mb and used that mfs
> >>>
> >>>a) Can someone provide me hints on what could be
> >>
> >>the
> >>
> >>>problem ?
> >>> 
> >>
> >>I use R5.3. According to the man page mdconfig(8)
> a
> >>md of type
> >>malloc should use "-o reserve", if it is large and
> >>to be "filled"
> >>(I think the man page means "filled quickly"):
> >>  "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."
> >>
> >>Maybe that helps?
> >>
> >>Did you try type "swap"?
> >>
> >>-Arne
> >>
> >>
> >>
> >>		
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> >> 
> > 
> > 
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