crush: add get_rule_weight_map

Calculate a weight map of OSDs for a given rule.

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

diff --git a/src/crush/CrushWrapper.cc b/src/crush/CrushWrapper.cc
index 52730a1d3903fd1ca5dbda650614ac65d1b1d1bd..43a525a1b1b9cb40cc4a5878c1f5bd543a8f75da 100644 (file)
--- a/src/crush/CrushWrapper.cc
+++ b/src/crush/CrushWrapper.cc
@@ -794,6 +794,52 @@ int CrushWrapper::add_simple_ruleset(string name, string root_name,
   return rno;
 }
 
+int CrushWrapper::get_rule_weight_map(unsigned ruleno, map<int,float> *pmap)
+{
+  if (ruleno >= crush->max_rules)
+    return -ENOENT;
+  if (crush->rules[ruleno] == NULL)
+    return -ENOENT;
+  crush_rule *rule = crush->rules[ruleno];
+
+  // build a weight map for each TAKE in the rule, and then merge them
+  for (unsigned i=0; i<rule->len; ++i) {
+    map<int,float> m;
+    float sum = 0;
+    if (rule->steps[i].op == CRUSH_RULE_TAKE) {
+      int n = rule->steps[i].arg1;
+      if (n >= 0) {
+       m[n] = 1.0;
+       sum = 1.0;
+      } else {
+       list<int> q;
+       q.push_back(n);
+       while (!q.empty()) {
+         int bno = q.front();
+         q.pop_front();
+         crush_bucket *b = crush->buckets[-1-bno];
+         assert(b);
+         for (unsigned j=0; j<b->size; ++j) {
+           float w = crush_get_bucket_item_weight(b, j);
+           m[b->items[j]] = w;
+           sum += w;
+         }
+       }
+      }
+    }
+    for (map<int,float>::iterator p = m.begin(); p != m.end(); ++p) {
+      map<int,float>::iterator q = pmap->find(p->first);
+      if (q == pmap->end()) {
+       (*pmap)[p->first] = p->second / sum;
+      } else {
+       q->second += p->second / sum;
+      }
+    }
+  }
+
+  return 0;
+}
+
 int CrushWrapper::remove_rule(int ruleno)
 {
   if (ruleno >= (int)crush->max_rules)

diff --git a/src/crush/CrushWrapper.h b/src/crush/CrushWrapper.h
index 0a633a51f5cba4fc51bf1c21460873c7a95fdca7..bc7bf9b9c91d49a628c4494058f55df3f49c9180 100644 (file)
--- a/src/crush/CrushWrapper.h
+++ b/src/crush/CrushWrapper.h
@@ -631,6 +631,18 @@ public:
     return s->arg2;
   }
 
+  /**
+   * calculate a map of osds to weights for a given rule
+   *
+   * Generate a map of which OSDs get how much relative weight for a
+   * given rule.
+   *
+   * @param ruleno [in] rule id
+   * @param pmap [out] map of osd to weight
+   * @return 0 for success, or negative error code
+   */
+  int get_rule_weight_map(unsigned ruleno, map<int,float> *pmap);
+
   /* modifiers */
   int add_rule(int len, int ruleset, int type, int minsize, int maxsize, int ruleno) {
     if (!crush) return -ENOENT;

diff --git a/src/test/crush/TestCrushWrapper.cc b/src/test/crush/TestCrushWrapper.cc
index d70a52540f5984e943199f7f14dbf2b3ca444d32..7d42da5030241c3189b28fd3c5223b6984f7577c 100644 (file)
--- a/src/test/crush/TestCrushWrapper.cc
+++ b/src/test/crush/TestCrushWrapper.cc
@@ -538,6 +538,11 @@ TEST(CrushWrapper, dump_rules) {
              ss.str().find("<item_name>default</item_name></step>"));
   }
 
+  map<int,float> wm;
+  c->get_rule_weight_map(0, &wm);
+  ASSERT_TRUE(wm.size() == 1);
+  ASSERT_TRUE(wm[0] == 1.0);
+
   delete c;
 }