doc: add the description for min_read_recency_for_promote

This cache tiering option is introduced in proxy read.

Signed-off-by: Zhiqiang Wang <zhiqiang.wang@intel.com>

diff --git a/doc/dev/cache-pool.rst b/doc/dev/cache-pool.rst
index 5fa910f98355fb2fb62e67ca35df5aa56c8f8b24..718a2b325408a51a012a617e237f172c62fca25f 100644 (file)
--- a/doc/dev/cache-pool.rst
+++ b/doc/dev/cache-pool.rst
@@ -55,6 +55,7 @@ Set the target size and enable the tiering agent for foo-hot::
  ceph osd pool set foo-hot hit_set_count 1
  ceph osd pool set foo-hot hit_set_period 3600   # 1 hour
  ceph osd pool set foo-hot target_max_bytes 1000000000000  # 1 TB
+ ceph osd pool set foo-hot min_read_recency_for_promote 1
 
 Drain the cache in preparation for turning it off::
 
@@ -112,6 +113,17 @@ evict cache objects, all hit_set_count HitSets are loaded into RAM.
 Currently there is minimal benefit for hit_set_count > 1 since the
 agent does not yet act intelligently on that information.
 
+The ``min_read_recency_for_promote`` defines how many HitSets to check for the
+existence of an object when handling a read operation. The checking result is
+used to decide whether to promote the object asynchronously. Its value should be
+between 0 and ``hit_set_count``. If it's set to 0, the object is always promoted.
+If it's set to 1, the current HitSet is checked. And if this object is in the
+current HitSet, it's promoted. Otherwise not. For the other values, the exact
+number of archive HitSets are checked. The object is promoted if the object is
+found in any of the most recent ``min_read_recency_for_promote`` HitSets. ::
+
+ ceph osd pool set {cachepool} min_read_recency_for_promote 1
+
 Cache mode
 ~~~~~~~~~~
 

diff --git a/doc/rados/operations/cache-tiering.rst b/doc/rados/operations/cache-tiering.rst
index 355d9369b6e921c64124cd4e6b8fc02c3d48ed02..e77137e7dc87c4af4471033adbefa9f2bce8f9f8 100644 (file)
--- a/doc/rados/operations/cache-tiering.rst
+++ b/doc/rados/operations/cache-tiering.rst
@@ -186,6 +186,17 @@ Binning accesses over time allows Ceph to determine whether a Ceph client
 accessed an object at least once, or more than once over a time period 
 ("age" vs "temperature").
 
+The ``min_read_recency_for_promote`` defines how many HitSets to check for the
+existence of an object when handling a read operation. The checking result is
+used to decide whether to promote the object asynchronously. Its value should be
+between 0 and ``hit_set_count``. If it's set to 0, the object is always promoted.
+If it's set to 1, the current HitSet is checked. And if this object is in the
+current HitSet, it's promoted. Otherwise not. For the other values, the exact
+number of archive HitSets are checked. The object is promoted if the object is
+found in any of the most recent ``min_read_recency_for_promote`` HitSets. ::
+
+       ceph osd pool set {cachepool} min_read_recency_for_promote 1
+
 .. note:: The longer the period and the higher the count, the more RAM the
    ``ceph-osd`` daemon consumes.  In particular, when the agent is active to 
    flush or evict cache objects, all ``hit_set_count`` HitSets are loaded