Messages in this thread | | | Subject | Re: Memory Management - BSD vs Linux | Date | Tue, 12 Aug 1997 08:43:43 +0200 (MET DST) | From | (Rogier Wolff) |
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Noel Maddy wrote: > > On 11 Aug 1997, Darren Reed wrote: > > In some mail I received from Theodore Y. Ts'o, sie wrote > > > > > > [3] Can any of these systems have > > > a) swap files rather than partitions > > > b) dynamically growing swap space? > > > As far as I can make out, the answeris no! > > > > > > Linux can swap to files (multiple files if necessary), and there is a > > > user-mode daemon that can allow you to dyanmically grow swap space (by > > > allocating a new file). > > > > NetBSD has swapfiles and does not require a daemon to be running for more > > to be added. NetBSD has also since moved on from just swap(2) to having > > swapctl(2) which supports things like swap files/partitions with different > > priorities and a replacement program for swapon - swapctl(8). > > Do you mean that NetBSD monitors the available swap space and > automatically adds more without a daemon, or just that more swap space > can be added via swapctl without a daemon running? Linux does the > latter without a daemon--the daemon Ted mentioned does the former.
There is a thing here.
The kernel already knows how to swap to a file. The kernel already knows how to "grow" a file. What wouldn't be too hard to implement is:
on "out of swap space" call the "grow file" function for the swap file, and try again.
A slight complication is that Linux uses a swap space signature which includes the size of the swap file. Writing that back can be considered dangerous.
Roger.
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