On Mon, May 12, 2014 at 12:38:19PM -0400, Dan Streetman wrote: > Add plist_requeue(), which moves the specified plist_node after > all other same-priority plist_nodes in the list. This is > essentially an optimized plist_del() followed by plist_add(). > > This is needed by swap, which (with the next patch in this set) > uses a plist of available swap devices. When a swap device > (either a swap partition or swap file) are added to the system > with swapon(), the device is added to a plist, ordered by > the swap device's priority. When swap needs to allocate a page > from one of the swap devices, it takes the page from the first swap > device on the plist, which is the highest priority swap device. > The swap device is left in the plist until all its pages are > used, and then removed from the plist when it becomes full. > > However, as described in man 2 swapon, swap must allocate pages > from swap devices with the same priority in round-robin order; > to do this, on each swap page allocation, swap uses a page from > the first swap device in the plist, and then calls plist_requeue() > to move that swap device entry to after any other same-priority > swap devices. The next swap page allocation will again use a > page from the first swap device in the plist and requeue it, > and so on, resulting in round-robin usage of equal-priority > swap devices. > > Also add plist_test_requeue() test function, for use by plist_test() > to test plist_requeue() function. > > Signed-off-by: Dan Streetman <ddstreet@xxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxx> > Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Acked-by: Mel Gorman <mgorman@xxxxxxx> -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>