mgr/pg_autoscaler: apply bias to pg_num selection

This is a relatively naive way to apply the bias: we just multiply it
to whatever we would have chosen.  A more clever approach would be to
factor this into the overall cluster-wide PG budget, so that biasing one
pool's PGs up would put downward pressure on other pools.  That is
significantly more complicated, however, and (I think) not worth the
effort.

Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/src/pybind/mgr/pg_autoscaler/module.py b/src/pybind/mgr/pg_autoscaler/module.py
index 136544409bd9c87c3758f1cf75f0424ac4160a6b..99530b3ba67c4877589a0d75a7db3813896f3dc3 100644 (file)
--- a/src/pybind/mgr/pg_autoscaler/module.py
+++ b/src/pybind/mgr/pg_autoscaler/module.py
@@ -269,6 +269,7 @@ class PgAutoscaler(MgrModule):
             raw_used_rate = osdmap.pool_raw_used_rate(pool_id)
 
             pool_logical_used = pool_stats[pool_id]['bytes_used']
+            bias = p['options'].get('pg_autoscale_bias', 1.0)
             target_bytes = p['options'].get('target_size_bytes', 0)
 
             # What proportion of space are we using?
@@ -282,16 +283,17 @@ class PgAutoscaler(MgrModule):
             final_ratio = max(capacity_ratio, target_ratio)
 
             # So what proportion of pg allowance should we be using?
-            pool_pg_target = (final_ratio * root_map[root_id].pg_target) / raw_used_rate
+            pool_pg_target = (final_ratio * root_map[root_id].pg_target) / raw_used_rate * bias
 
             final_pg_target = max(p['options'].get('pg_num_min', PG_NUM_MIN),
                                   nearest_power_of_two(pool_pg_target))
 
-            self.log.info("Pool '{0}' root_id {1} using {2} of space, "
-                          "pg target {3} quantized to {4} (current {5})".format(
+            self.log.info("Pool '{0}' root_id {1} using {2} of space, bias {3}, "
+                          "pg target {4} quantized to {5} (current {6})".format(
                               p['pool_name'],
                               root_id,
                               final_ratio,
+                              bias,
                               pool_pg_target,
                               final_pg_target,
                               p['pg_num_target']