Re: [announce] swap mini-howto

[Jeff Garzik <jgarzik@pobox.com>]

Andrew Morton wrote:

>Something I'd like to point out here:  in 2.4 and earlier, swapfiles
>are less robust than swap devices - the need to go and read metadata
>from the filesystem made them prone to oom deadlocks allocating pages
>and buffer_heads with which to perform the swapout.
>
>That has changed in 2.5.  Swapping onto a regular file has no
>disadvantage wrt swapping onto a block device.  The kernel does
>not need to allocate any memory at all to get a swapcache page
>onto disk.
>
>Which is interesting.  Because swapfiles are much easier to administer,
>and much easier to stripe.  Adding, removing and resizing is simplified.
>Distributors of 2.6-based kernels could consider doing away with
>swapdevs altogether.
>  
>

That said, I would like to again point out that using sparse swapfiles 
should still be discouraged.  It may be supported, but it's much better 
for system performance and stability, IMO, if the sysadmin makes certain 
all swapfiles are 100% allocated before they are mentioned to the swap 
subsystem.

    Jeff