On Fri, Jan 15, 2016 at 2:25 AM, Seth Arnold <seth.arn...@canonical.com> wrote: > On Thu, Jan 14, 2016 at 12:27:58PM +0200, Dustin Kirkland wrote: >> Moreover, just 'sudo apt-get install swapspace' and watch as swapfiles >> are created/deleted as needed. If your root disk is lvm-encrypted, >> then obviously such swap files are encrypted, too. > > I've been severely skeptical of the swapspace package: > > - Swap is used when the system is already under pressure; a few hundred > megs is great and probably for the best but if the system is actively > pushing beyond that then it's being pushed too hard. > > - If the swap space is going to be allocated on the fly, that means the > disk blocks have to zeroed on the fly, when the system is under > pressure, rather than at some leisurely time beforehand. > > - If the swap space is allocated on a filesystem, it's probably being > allocated from a fragmented filesystem that's 90% full rather than a > nice contiguous block of space as it would with a swap partition. > > - Accessing further into a file may involve loading multiple indirect > blocks from disk into unswappable kernel memory. A swap partition does > not require indirection blocks. > > - If the swap space allocated from a filesystem pushes the filesystem to > 95% full (or whatever is left after accounting for reserved blocks), > programs will error and almost nothing handles "disk full" errors > gracefully. Swap partitions do not cause surprise gigabyte losses in > free space. > > - Swap files can't be allocated from btrfs filesystems and probably > shouldn't be allocated from zfs filesystems either. (Swap on zvols, > maybe.) > > Perhaps the swapspace package uses some tasteful tunables to mitigate > against my concerns but the end result is that it contributes extra load, > extra IO pressure, and extra uncertainty at a time when the system is > already experiencing too much load, too much IO pressure, and too much > uncertainty. > > The risks and downsides of swapspace feel like a lot compared to the > slight hassle of having the installer make a swap partition.
I count 4 "if's", 3 "probably's", 2 "should/would's", and 1 "maybe" in that reply :-) Perhaps try it out? I've been running it and /tmp on tmpfs for several years (since before ~precise) on my desktop on an encrypted LVM partition. My machine has a lot of memory (16GB), though I do push it hard), and have never noticed a swapspace-related problem. I've also used this combination on hundreds of servers, and several production systems. Here's /etc/swapspace.conf, with its tunables... http://paste.ubuntu.com/14516155/ -- ubuntu-devel mailing list ubuntu-devel@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel