Description of problem:
On high order memory allocations kswapd evicts a lot of pages to the encrypted swap sometimes what causes long desktop pauses (mouse cursor, music playing stops). The system completely unusable until the hard disk has been flushed everything to the swap. The pause can be really long, up to 1 minute.
(The high order allocation because of cifs, see bug#617795)
I've vm.swappiness=0 and vm.min_free_kbytes=67584 setting in /etc/sysctl.conf. Swap is on LVM top of dm-crypt top of a high-performance SSD disk.
I'd like to hear flawless music playing under the swapping-out too.
Version-Release number of selected component (if applicable):
Make swap, fill the memory with usual memory-hungry desktop applications like gimp, firefox, netbeans, openoffice, make the free memory fragmented with updatedb and then try to allocate some high order pages (eg.: modprobe cifs CIFSMaxBufSize=128000). The desktop will freeze for a while.
If I remember correctly this issue doesn't depend on the encryption.
dstat log is at https://bugzilla.redhat.com/attachment.cgi?id=434098
/dev/mapper/luks-6eb56688-2689-49f6-8de4-6b30a0fb7cf2 is active:
keysize: 128 bits
I think this problem has been solved by upstream in kernel 2.6.38 as memory compaction replaced lumpy reclaim.