FS-Cache: Add use of /proc and presentation of statistics

Make FS-Cache create its /proc interface and present various statistical
information through it.  Also provide the functions for updating this
information.

These features are enabled by:

	CONFIG_FSCACHE_PROC
	CONFIG_FSCACHE_STATS
	CONFIG_FSCACHE_HISTOGRAM

The /proc directory for FS-Cache is also exported so that caching modules can
add their own statistics there too.

The FS-Cache module is loadable at this point, and the statistics files can be
examined by userspace:

	cat /proc/fs/fscache/stats
	cat /proc/fs/fscache/histogram

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/fs/fscache/Kconfig b/fs/fscache/Kconfig
index 7c7bccd5eee4..9bbb8ce7bea0 100644
--- a/fs/fscache/Kconfig
+++ b/fs/fscache/Kconfig
@@ -11,6 +11,40 @@ config FSCACHE
 
           See Documentation/filesystems/caching/fscache.txt for more information.
 
+config FSCACHE_STATS
+        bool "Gather statistical information on local caching"
+        depends on FSCACHE && PROC_FS
+        help
+          This option causes statistical information to be gathered on local
+          caching and exported through file:
+
+                /proc/fs/fscache/stats
+
+          The gathering of statistics adds a certain amount of overhead to
+          execution as there are a quite a few stats gathered, and on a
+          multi-CPU system these may be on cachelines that keep bouncing
+          between CPUs.  On the other hand, the stats are very useful for
+          debugging purposes.  Saying 'Y' here is recommended.
+
+          See Documentation/filesystems/caching/fscache.txt for more information.
+
+config FSCACHE_HISTOGRAM
+        bool "Gather latency information on local caching"
+        depends on FSCACHE && PROC_FS
+        help
+          This option causes latency information to be gathered on local
+          caching and exported through file:
+
+                /proc/fs/fscache/histogram
+
+          The generation of this histogram adds a certain amount of overhead to
+          execution as there are a number of points at which data is gathered,
+          and on a multi-CPU system these may be on cachelines that keep
+          bouncing between CPUs.  On the other hand, the histogram may be
+          useful for debugging purposes.  Saying 'N' here is recommended.
+
+          See Documentation/filesystems/caching/fscache.txt for more information.
+
 config FSCACHE_DEBUG
         bool "Debug FS-Cache"
         depends on FSCACHE