Module Name: src
Committed By: pooka
Date: Sun Jun 15 12:58:01 UTC 2014
Modified Files:
src/sys/rump/librump/rumpkern: vm.c
Log Message:
update comment
To generate a diff of this commit:
cvs rdiff -u -r1.158 -r1.159 src/sys/rump/librump/rumpkern/vm.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/rump/librump/rumpkern/vm.c
diff -u src/sys/rump/librump/rumpkern/vm.c:1.158 src/sys/rump/librump/rumpkern/vm.c:1.159
--- src/sys/rump/librump/rumpkern/vm.c:1.158 Fri Jun 13 11:53:48 2014
+++ src/sys/rump/librump/rumpkern/vm.c Sun Jun 15 12:58:01 2014
@@ -1,4 +1,4 @@
-/* $NetBSD: vm.c,v 1.158 2014/06/13 11:53:48 pooka Exp $ */
+/* $NetBSD: vm.c,v 1.159 2014/06/15 12:58:01 pooka Exp $ */
/*
* Copyright (c) 2007-2011 Antti Kantee. All Rights Reserved.
@@ -41,7 +41,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vm.c,v 1.158 2014/06/13 11:53:48 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vm.c,v 1.159 2014/06/15 12:58:01 pooka Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
@@ -478,9 +478,15 @@ static LIST_HEAD(, pagerinfo) pagerlist
/*
* Pager "map" in routine. Instead of mapping, we allocate memory
- * and copy page contents there. Not optimal or even strictly
- * correct (the caller might modify the page contents after mapping
- * them in), but what the heck. Assumes UVMPAGER_MAPIN_WAITOK.
+ * and copy page contents there. The reason for copying instead of
+ * mapping is simple: we do not assume we are running on virtual
+ * memory. Even if we could emulate virtual memory in some envs
+ * such as userspace, copying is much faster than trying to awkardly
+ * cope with remapping (see "Design and Implementation" pp.95-98).
+ * The downside of the approach is that the pager requires MAXPHYS
+ * free memory to perform paging, but short of virtual memory or
+ * making the pager do I/O in page-sized chunks we cannot do much
+ * about that.
*/
vaddr_t
uvm_pagermapin(struct vm_page **pgs, int npages, int flags)
