D22256.id63991.diff
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D22256.id63991.diff
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	Index: sys/vm/swap_pager.c
	===================================================================
	--- sys/vm/swap_pager.c
	+++ sys/vm/swap_pager.c
	@@ -985,7 +985,18 @@
	* Transfer source to destination.
	*/
	swp_pager_init_freerange(&s_free, &n_free);
	- for (i = 0; i < dstobject->size; ++i) {
	+
	+ /*
	+ * Search srcobject pindex of corresponding dstobject between 0 and
	+ * dstobject->size to transfer.
	+ *
	+ * Based on experiments, about 80% to 95% of vm_indexes are
	+ * SWAPBLK_NONE. Calling swap_pager_find_least() adds extra
	+ * pctrie lookups. However, skipping SWAPBLK_NONE gives us saving
	+ * of pctrie lookups in total.
	+ */
	+ for (i = 0; (i = swap_pager_find_least(srcobject, i + offset) - offset)
	+ < dstobject->size; ++i) {
	srcaddr = swp_pager_meta_ctl(srcobject, i + offset, SWM_POP);
	if (srcaddr == SWAPBLK_NONE)
	continue;