config-ref: add a note on current scheduler settings.

Adding a note on configuirables for max concurrent requests and the rest of
experimental options for tuning dmclock scheduler

Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>

diff --git a/doc/radosgw/config-ref.rst b/doc/radosgw/config-ref.rst
index 37bb8eea9007e3229dc007d7af5f9bafa98c179e..6c80663dbad5a27f9823ce8eacacdb583be20bb6 100644 (file)
--- a/doc/radosgw/config-ref.rst
+++ b/doc/radosgw/config-ref.rst
@@ -943,6 +943,65 @@ Barbican Settings
 :Default: None
 
 
+QoS settings
+------------
+
+.. versionadded:: Nautilus
+
+The ``civetweb`` frontend has a threading model that uses a thread per
+connection and hence automatically throttled by ``rgw thread pool size``
+configurable when it comes to accepting connections. The ``beast`` frontend is
+not restricted by the thread pool size when it comes to accepting new
+connections, so a scheduler abstraction is introduced in Nautilus release which
+for supporting ways for scheduling requests in the future.
+
+Currently the scheduler defaults to a throttler which throttles the active
+connections to a configured limit. QoS based on mClock is currently in an
+*experimental* phase and not recommended for production yet. Current
+implementation of *dmclock_client* op queue divides RGW Ops on admin, auth
+(swift auth, sts) metadata & data requests.
+
+
+``rgw max concurrent requests``
+
+:Description: Maximum number of concurrent HTTP requests that the beast frontend
+              will process. Tuning this can help to limit memory usage under
+              heavy load.
+:Type: Integer
+:Default: 1024
+
+
+``rgw scheduler type``
+
+:Description: The type of RGW Scheduler to use. Valid values are throttler,
+              dmclock. Currently defaults to throttler which throttles beast
+              frontend requests. dmclock is *experimental* and will need the
+              experimental flag set
+
+
+The options below are to tune the experimental dmclock scheduler. op_class for
+the flags below is one of admin, auth, metadata or data
+
+``rgw_dmclock_<op_class>_res``
+
+:Description: The mclock reservation for `op_class` requests
+:Type: float
+:Default: 100.0
+
+``rgw_dmclock_<op_class>_wgt``
+
+:Description: The mclock weight for `op_class` requests
+:Type: float
+:Default: 1.0
+
+``rgw_dmclock_<op_class>_lim``
+
+:Description: The mclock limit for `op_class` requests
+:Type: float
+:Default: 0.0
+
+
+
 .. _Architecture: ../../architecture#data-striping
 .. _Pool Configuration: ../../rados/configuration/pool-pg-config-ref/
 .. _Cluster Pools: ../../rados/operations/pools