Lock cancellation can be very time consuming when there are many pages under a lock.

One easy area for improvement is the osc_page_gang_lookup callback functions - These work on individual pages from an array, but they can be trivially modified to work on the entire array at once, reducing overhead.

I've got a simple patch for this, which improves performance of lock cancellation by about 10%, and truncate [when pages are in cache] (which also uses the call back) by about 5%.