Date: Wed, 14 Dec 2016 23:36:32 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r310098 - head/sys/vm Message-ID: <201612142336.uBENaWX7076903@repo.freebsd.org>
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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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