using mfs of size > 64Mb and system stability

[Poul-Henning Kamp]

In message <20050110135747.GA44905 at xor.obsecurity.org>, Kris Kennaway writes:
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>On Mon, Jan 10, 2005 at 11:11:44AM +0100, Poul-Henning Kamp wrote:
>> In message <20050110100840.29845.qmail at web30301.mail.mud.yahoo.com>, Bara=
>th S w
>> rites:
>> >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.
>>=20
>> malloc backing should not be used for large disks.
>>=20
>> If you _truly_ want to have a large disk which is memory backed,
>> you should consider using the "preload" backing as this will withdraw
>> the memory entirely from the kernels use.
>>=20
>> In general, the benefit from using RAM disks is much smaller than
>> most people realize.
>
>I've found that using a swap-backed disk substantially cuts back on
>disk accesses for my purposes [...]

Swap-backing is very different from RAM disks in that things get
pushed out of RAM if better use can be made of the pages.

With RAM disks (preload or malloc backing) you occupy valuable
RAM pages with free diskblocks.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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