Create basic directory structure

All new features specs go into in_progress directory.
Once signed off, it should be moved to done directory.

For now,
This change moves all the Gluster 4.0 feature specs to
in_progress. All other specs are under done/release-version.

More cleanup required will be done incrementally.

Change-Id: Id272d301ba8c434cbf7a9a966ceba05fe63b230d
BUG: 1206539
Signed-off-by: Raghavendra Talur <rtalur@redhat.com>
Reviewed-on: http://review.gluster.org/11969
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>
Reviewed-by: Prashanth Pai <ppai@redhat.com>
Tested-by: Humble Devassy Chirammal <humble.devassy@gmail.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/done/Features/memory-usage.md b/done/Features/memory-usage.md
new file mode 100644
index 0000000..4e1a8a0
--- /dev/null
+++ b/done/Features/memory-usage.md
@@ -0,0 +1,49 @@
+object expiry tracking memroy usage
+====================================
+
+Bitrot daemon tracks objects for expiry in a data structure known
+as "timer-wheel" (after which the object is signed). It's a well
+known data structure for tracking million of objects of expiry.
+Let's see the memory usage involved when tracking 1 million
+objects (per brick).
+
+Bitrot daemon uses "br_object" structure to hold information
+needed for signing. An instance of this structure is allocated
+for each object that needs to be signed.
+
+                struct br_object {
+                        xlator_t *this;
+                
+                        br_child_t *child;
+                
+                        void *data;
+                        uuid_t gfid;
+                        unsigned long signedversion;
+                
+                        struct list_head list;
+                };
+
+Timer-wheel requires an instance of the structure below per
+object that needs to be tracked for expiry.
+
+                struct gf_tw_timer_list {
+                        void *data;
+                        unsigned long expires;
+                
+                        /** callback routine */
+                        void (*function)(struct gf_tw_timer_list *, void *, unsigned long);
+                
+                        struct list_head entry;
+                };
+
+Structure sizes:
+
+-  sizeof (struct br_object): 64 bytes
+-  sizeof (struct gf_tw_timer_list): 40 bytes
+
+Together, these structures take up 104 bytes. To track all 1 million objects
+at the same time, the amount of memory taken up would be:
+
+** 1,000,000 * 104 bytes: ~100MB**
+
+Not so bad, I think.