32GB limit per swap device?
daniel at digsys.bg
Wed Aug 10 10:44:05 UTC 2011
On 10.08.11 11:47, Jeremy Chadwick wrote:
> So we're back to where we started: swap slices/partitions can be
> greater than 32GBytes in size, but "something" is limiting the maximum
> amount of memory which can be dumped to a single swap swap to 32GBytes.
It seems there is still some confusion. Partition size(s) is 64GB, but
FreeBSD will use only 32GB of that for swap.
Produces 64GB dump, but.. I can't see the dump on the swap device
(savecore doesn't find the magic number). My swap device is gmirror or
two slices (/dev/mirror/swap).
Removing the gmirror and listing both slices for swap .. works.
I could use separate device for dumps, but the disk real estate on this
particular blade is limited...
Well, I really asked two questions:
Q1: Is FreeBSD still limited to 32GB per swap slice?
A1: yes. There is limit set in /usr/src/sys/vm/swap_pager.c
Q2: If FreeBSD will only use 32GB of the slice for swap, will it dump
larger (64GB in my case) core in there?
A2b: If the swap slice is gmirrored, you don't get any dump back.
I believe the gmirror bug might exist in smaller partitions as well, but
haven't tested it yet (have few such systems that never duped core). It
does not matter if I do full dump or minidump: on gmirrored 64GB
partittion savecore does not find anything.
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