From d7be93f61f54ec4deb27f147693b949ca531e0bb Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Tue, 16 Feb 2010 11:27:55 -0800
Subject: [PATCH] kernel - tmpfs - Remove warning message on mount, update
 manual page

* Remove the warning message on mount.

* Improve the manual page.
---
 share/man/man5/tmpfs.5       | 52 +++++++++++++++++++++++++++++++-------------
 sys/vfs/tmpfs/tmpfs_vfsops.c |  3 ---
 2 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/share/man/man5/tmpfs.5 b/share/man/man5/tmpfs.5
index a8126369c6..83541e87b9 100644
--- a/share/man/man5/tmpfs.5
+++ b/share/man/man5/tmpfs.5
@@ -46,14 +46,6 @@ module at boot time, place the following line in
 .Bd -literal -offset indent
 tmpfs_load="YES"
 .Ed
-.Sh DESCRIPTION
-The
-.Nm
-driver will permit the
-.Dx
-kernel to access
-.Tn tmpfs
-file systems.
 .Sh OPTIONS
 The following options are available when
 mounting
@@ -73,6 +65,40 @@ maximum size (in bytes) for the file system.
 .It Cm maxfilesize
 maximum file size (in bytes).
 .El
+.Sh DESCRIPTION
+In the
+.Dx
+implementation,
+.Nm
+filesystems are backed by swap space.
+Only memory pressure will cause data to be backed to swap.
+Normal filesystem operations such as fsync(), buffer cache flushing,
+and vnode recycling have no effect.
+.Pp
+.Nm
+stores meta-data in wired kernel memory.  Meta-data is not backed by
+swap so care must be taken if using
+.Nm
+to store large numbers of small files.
+.Pp
+It is recommended that a large amount of swap space be reserved on modern
+.Dx
+platforms to accomodate
+.Nm
+and other subsystems.
+32-bit kernels can accomodate 32G of swap by default while 64-bit kernels
+can accomodate 512G of swap by default.
+These defaults can be increased though it should be noted that 32-bit
+kernels are ultimately limited by the amount of KVM available in its
+small 32-bit address space.
+.Pp
+.Nm
+will allocate and deallocate swap backing store on the fly based on usage.
+By default
+.Nm
+allows up to 100% of swap space to be used.
+If this is not desireable then the size option should be used to limit
+its size.
 .Sh EXAMPLES
 To mount a
 .Nm
@@ -83,7 +109,8 @@ memory file system:
 .Xr nmount 2 ,
 .Xr unmount 2 ,
 .Xr fstab 5 ,
-.Xr mount 8
+.Xr mount 8 ,
+.Xr swapcache 8
 .Sh HISTORY
 The
 .Nm
@@ -112,9 +139,4 @@ to
 This manual page was written by
 .An Xin LI Aq delphij@FreeBSD.org .
 .Sh BUGS
-The
-.Nm
-kernel implementation is currently considered as
-an experimental feature.
-Some file system mount
-time options are not well supported.
+Hopefully not.
diff --git a/sys/vfs/tmpfs/tmpfs_vfsops.c b/sys/vfs/tmpfs/tmpfs_vfsops.c
index 338ede673a..66179d99f7 100644
--- a/sys/vfs/tmpfs/tmpfs_vfsops.c
+++ b/sys/vfs/tmpfs/tmpfs_vfsops.c
@@ -200,9 +200,6 @@ tmpfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
 		return EOPNOTSUPP;
 	}
 
-	kprintf("WARNING: TMPFS is considered to be a highly experimental "
-	    "feature in DragonFly.\n");
-
 	/* Do not allow mounts if we do not have enough memory to preserve
 	 * the minimum reserved pages. */
 	mem_size = vmstats.v_free_count + vmstats.v_inactive_count + get_swpgtotal();
-- 
2.11.4.GIT