From f94a44e688883f2db0971435a5333a8b60c77dec Mon Sep 17 00:00:00 2001
From: Josh Durgin <josh.durgin@dreamhost.com>
Date: Thu, 20 Oct 2011 17:13:21 -0700
Subject: [PATCH] OSDMonitor: reweight towards average utilization

The existing reweight-by-utilization calculation did not take into
account the current weight of an OSD, and depended in part on the
threshold given by the user. Also send the user both the old and new
weights.

Fixes: #1636
Signed-off-by: Josh Durgin <josh.durgin@dreamhost.com>
---
 src/mon/OSDMonitor.cc | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/mon/OSDMonitor.cc b/src/mon/OSDMonitor.cc
index adc0cd1268d..0945c3e9247 100644
--- a/src/mon/OSDMonitor.cc
+++ b/src/mon/OSDMonitor.cc
@@ -172,7 +172,7 @@ int OSDMonitor::reweight_by_utilization(int oload, std::string& out_str)
   }
 
   // Avoid putting a small number (or 0) in the denominator when calculating
-  // average_full
+  // average_util
   const PGMap &pgm = mon->pgmon()->pg_map;
   if (pgm.osd_sum.kb < 1024) {
     ostringstream oss;
@@ -192,32 +192,34 @@ int OSDMonitor::reweight_by_utilization(int oload, std::string& out_str)
     return -EDOM;
   }
 
-  // Assign a lower weight to overloaded OSDs
-  float average_full = pgm.osd_sum.kb_used;
-  average_full /= pgm.osd_sum.kb;
-  float overload_full = average_full;
-  overload_full *= oload;
-  overload_full /= 100.0;
+  float average_util = pgm.osd_sum.kb_used;
+  average_util /= pgm.osd_sum.kb;
+  float overload_util = average_util * oload / 100.0;
 
   ostringstream oss;
   char buf[128];
-  snprintf(buf, sizeof(buf), "average_full: %04f, overload_full: %04f. ",
-	   average_full, overload_full);
+  snprintf(buf, sizeof(buf), "average_util: %04f, overload_util: %04f. ",
+	   average_util, overload_util);
   oss << buf;
   std::string sep;
   oss << "overloaded osds: ";
   for (hash_map<int,osd_stat_t>::const_iterator p = pgm.osd_stat.begin();
        p != pgm.osd_stat.end();
        ++p) {
-    float full = p->second.kb_used;
-    full /= p->second.kb;
-    if (full >= overload_full) {
+    float util = p->second.kb_used;
+    util /= p->second.kb;
+    if (util >= overload_util) {
       sep = ", ";
-      float new_weight = (1.0f - full) / (1.0f - overload_full);
+      // Assign a lower weight to overloaded OSDs. The current weight
+      // is a factor to take into account the original weights,
+      // to represent e.g. differing storage capacities
+      float weight = osdmap.get_weightf(p->first);
+      float new_weight = (average_util / util) * weight;
       osdmap.set_weightf(p->first, new_weight);
       char buf[128];
-      snprintf(buf, sizeof(buf), "%d [%04f]", p->first, new_weight);
-      oss << sep << buf;
+      snprintf(buf, sizeof(buf), "%d [%04f -> %04f]", p->first,
+	       weight, new_weight);
+      oss << buf << sep;
     }
   }
   if (sep.empty()) {