doc: Updated release notes for several features/changes in 3.11.0

Updates #61, Updates #156
Fixes #166, Fixes #167

Change-Id: I031bf944493b959d44c97fb0ddf7c1b80e53bdda
Signed-off-by: Shyam <srangana@redhat.com>
Reviewed-on: https://review.gluster.org/17390
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>

doc/release-notes/3.11.0.md

@@ -43,9 +43,16 @@ None
 ### Several memory leaks are fixed in gfapi during graph switches
 *Notes for users:*
 
+Gluster API (or gfapi), has had a few memory leak issues arising specifically
+during changes to volume graphs (volume topology or options). A few of these are
+addressed in this release, and more work towards ironing out the pending leaks
+are in the works across the next few releases.
+
 *Limitations:*
+None
 
 *Known Issues:*
+None
 
 ### get-state CLI is enhanced to provide client and brick capacity related information
 *Notes for users:*
@@ -103,16 +110,44 @@ None
 ### Feature for metadata-caching/small file performance is production ready
 *Notes for users:*
 
+Over the course of releases several fixes and enhancements have been made to
+the mdcache xlator, to improve performance of small file workloads. As a
+result, with this release we are announcing this feature to be production ready.
+
+In order to improve the performance of directory operations of Gluster volumes,
+the maximum metadata (stat, xattr) caching time on the client side is increased
+to 10 minutes, without compromising on the consistency of the cache. Significant
+performance improvements can be achieved in the following workloads on FUSE and
+SMB access, by enabling metadata caching:
+
+- Listing of directories (recursive)
+- Creating files
+- Deleting files
+- Renaming files
+
+To enable metadata caching execute the following commands:
+```bash
+# gluster volume set group metadata-cache
+# gluster volume set network.inode-lru-limit <n>
+```
+\<n\>, is set to 50000 by default. It should be increased if the number of
+concurrently accessed files in the volume is very high. Increasing this number
+increases the memory footprint of the brick processes.
+
 *Limitations:*
+None
 
 *Known Issues:*
+None
 
-### "Parallel Readdir" feature is production ready
+### "Parallel Readdir" feature introduced in 3.10.0 is production ready
 *Notes for users:*
 
-*Limitations:*
+This feature was introduced in 3.10 and was experimental in nature. Over the
+course of 3.10 minor releases and 3.11.0 release, this feature has been
+stabilized and is ready for use in production environments.
 
-*Known Issues:*
+For further release notes refer: [3.10.0 release notes](https://github.com/gluster/glusterfs/blob/release-3.10/doc/release-notes/3.10.0.md)
 
 ### Object versioning is enabled only if bitrot is enabled
 *Notes for users:*
@@ -152,9 +187,16 @@ None.
 ### Improved adoption of standard refcounting functions across the code
 *Notes for users:*
 
+This change does not impact users, it is an internal code cleanup activity
+that ensures that we ref count in a standard manner, thus avoiding unwanted
+bugs due to different implementations of the same.
+
 *Limitations:*
+None
 
 *Known Issues:*
+This standardization started with this release and is expected to continue
+across releases.
 
 ### Performance improvements to rebalance have been made
 *Notes for users:*