Author: kib
Date: Wed Dec 14 23:36:32 2016
New Revision: 310098
URL: https://svnweb.freebsd.org/changeset/base/310098
Log:
Provide introductory description of the default pager.
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Modified:
head/sys/vm/default_pager.c
Modified: head/sys/vm/default_pager.c
==============================================================================
--- head/sys/vm/default_pager.c Wed Dec 14 23:34:25 2016 (r310097)
+++ head/sys/vm/default_pager.c Wed Dec 14 23:36:32 2016 (r310098)
@@ -57,6 +57,16 @@ static boolean_t default_pager_haspage(v
/*
* pagerops for OBJT_DEFAULT - "default pager".
+ *
+ * This pager handles anonymous (no handle) swap-backed memory, just
+ * like the swap pager. It allows several optimizations based on the
+ * fact that no pages of a default object can be swapped out. The
+ * most important optimization is in vm_fault(), where the pager is
+ * never asked for a non-resident page. Instead, a freshly allocated
+ * zeroed page is used.
+ *
+ * On the first request to page out a page from a default object, the
+ * object is converted to swap pager type.
*/
struct pagerops defaultpagerops = {
.pgo_alloc = default_pager_alloc,
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