From:  <brian@localhost.localdomain>
Date: Mon, 21 Apr 2008 18:17:06 +0000 (-0700)
Subject: Fix for wheel algo to be dynamic
X-Git-Tag: _20~1^2~8
X-Git-Url: https://git.m6w6.name/?a=commitdiff_plain;h=83d63a1f916b073f8cf44cf91b6c0b3d118dabe5;p=m6w6%2Flibmemcached

Fix for wheel algo to be dynamic
---

diff --git a/ChangeLog b/ChangeLog
index 9b99aafa..effd1d13 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,5 @@
+  * Wheel uses less memory/dynamic allocation for size (no longer limited to
+    512 hosts by default.
   * memslap memory leak fix
   * Added Ketama distribution
   * Fix assert.h compile problem on CentOS
diff --git a/libmemcached/memcached.c b/libmemcached/memcached.c
index bcc0477d..b681f6cb 100644
--- a/libmemcached/memcached.c
+++ b/libmemcached/memcached.c
@@ -49,6 +49,14 @@ void memcached_free(memcached_st *ptr)
       free(ptr->continuum);
   }
 
+  if (ptr->wheel)
+  {
+    if (ptr->call_free)
+      ptr->call_free(ptr, ptr->wheel);
+    else
+      free(ptr->wheel);
+  }
+
   if (ptr->is_allocated == MEMCACHED_ALLOCATED)
   {
     if (ptr->call_free)
diff --git a/libmemcached/memcached.h b/libmemcached/memcached.h
index 45d4085f..935a4a13 100644
--- a/libmemcached/memcached.h
+++ b/libmemcached/memcached.h
@@ -81,7 +81,8 @@ struct memcached_st {
   memcached_hash hash;
   memcached_server_distribution distribution;
   void *user_data;
-  unsigned int wheel[MEMCACHED_WHEEL_SIZE];
+  unsigned int *wheel;
+  uint32_t wheel_count;
   uint32_t continuum_count;
   memcached_continuum_item_st *continuum;
   memcached_clone_func on_clone;
diff --git a/libmemcached/memcached_constants.h b/libmemcached/memcached_constants.h
index e60a03b7..1d2b08ad 100644
--- a/libmemcached/memcached_constants.h
+++ b/libmemcached/memcached_constants.h
@@ -19,7 +19,6 @@ extern "C" {
 #define MEMCACHED_MAX_BUFFER 8196
 #define MEMCACHED_MAX_HOST_LENGTH 64
 #define MEMCACHED_MAX_HOST_SORT_LENGTH 86 /* Used for Ketama */
-#define MEMCACHED_WHEEL_SIZE 1024
 #define MEMCACHED_POINTS_PER_SERVER 100 
 #define MEMCACHED_CONTINUUM_SIZE MEMCACHED_POINTS_PER_SERVER*100 /* This would then set max hosts to 100 */ 
 #define MEMCACHED_STRIDE 4
diff --git a/libmemcached/memcached_hash.c b/libmemcached/memcached_hash.c
index c0e928a1..4cb442cb 100644
--- a/libmemcached/memcached_hash.c
+++ b/libmemcached/memcached_hash.c
@@ -148,7 +148,7 @@ unsigned int dispatch_host(memcached_st *ptr, uint32_t hash)
     {
       unsigned int server_key;
 
-      server_key= hash % MEMCACHED_WHEEL_SIZE;
+      server_key= hash % MEMCACHED_STRIDE * ptr->wheel_count;
 
       return ptr->wheel[server_key];
     }
@@ -159,55 +159,8 @@ unsigned int dispatch_host(memcached_st *ptr, uint32_t hash)
     return hash % ptr->number_of_hosts;
   }
 
-  if (ptr->distribution == MEMCACHED_DISTRIBUTION_MODULA)
-  {
-    return hash % ptr->number_of_hosts;
-  }
-  else if (ptr->distribution == MEMCACHED_DISTRIBUTION_CONSISTENT)
-  {
-    unsigned int server_key;
-
-    server_key= hash % MEMCACHED_WHEEL_SIZE;
-
-    return ptr->wheel[server_key];
-  }
-  else if (ptr->distribution == MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA)
-  {
-    int num = ptr->number_of_hosts * MEMCACHED_POINTS_PER_SERVER;
-
-    hash = hash;
-    memcached_continuum_item_st *begin, *end, *left, *right, *middle;
-    begin = left = ptr->continuum;
-    end = right = ptr->continuum + (num - 1);
-    while(1)
-    {
-      middle = left + (right - left) / 2;
-      if(middle==end)
-      {
-        return begin->index;
-      }
-      if(middle==begin)
-      {
-        return end->index;
-      }
-      memcached_continuum_item_st *rmiddle = middle+1;
-      if(hash<rmiddle->value && hash>=middle->value)
-        return middle->index;
-
-      if(middle->value < hash) {
-        left = middle + 1;
-      }else if(middle->value > hash) {
-        right = middle - 1;
-      }
-
-      if (left>right)
-        return left->index;
-    }
-  } 
-  else 
-  {
-    WATCHPOINT_ASSERT(0);
-  }
+  WATCHPOINT_ASSERT(0); /* We should never reach here */
+  return 0;
 }
 
 unsigned int memcached_generate_hash(memcached_st *ptr, char *key, size_t key_length)
diff --git a/libmemcached/memcached_hosts.c b/libmemcached/memcached_hosts.c
index 72de6d09..03ea81e3 100644
--- a/libmemcached/memcached_hosts.c
+++ b/libmemcached/memcached_hosts.c
@@ -8,16 +8,32 @@ memcached_return update_continuum(memcached_st *ptr);
 
 #define MEMCACHED_WHEEL_SIZE 1024
 #define MEMCACHED_STRIDE 4
-static void rebalance_wheel(memcached_st *ptr)
+static memcached_return rebalance_wheel(memcached_st *ptr)
 {
   unsigned int x;
   unsigned int y;
   unsigned int latch;
 
+  if (ptr->number_of_hosts > ptr->wheel_count)
+  {
+    uint32_t *new_ptr;
+
+    if (ptr->call_realloc)
+      new_ptr= (uint32_t *)ptr->call_realloc(ptr, ptr->wheel, sizeof(uint32_t) * (ptr->number_of_hosts + MEMCACHED_CONTINUUM_ADDITION) * MEMCACHED_STRIDE);
+    else
+      new_ptr= (uint32_t *)realloc(ptr->wheel, sizeof(uint32_t) * (ptr->number_of_hosts + MEMCACHED_CONTINUUM_ADDITION) * MEMCACHED_STRIDE);
+
+    if (new_ptr == 0)
+      return MEMCACHED_MEMORY_ALLOCATION_FAILURE;
+
+    ptr->wheel= new_ptr;
+    ptr->wheel_count= ptr->number_of_hosts + MEMCACHED_CONTINUUM_ADDITION;
+  }
+
   /* Seed the Wheel */
-  memset(ptr->wheel, 0, sizeof(unsigned int) * MEMCACHED_WHEEL_SIZE);
+  memset(ptr->wheel, 0, sizeof(uint32_t) * MEMCACHED_STRIDE * ptr->wheel_count);
 
-  for (latch= y= x= 0; x < MEMCACHED_WHEEL_SIZE; x++, latch++)
+  for (latch= y= x= 0; x < MEMCACHED_STRIDE * ptr->wheel_count; x++, latch++)
   {
     if (latch == MEMCACHED_STRIDE)
     {
@@ -29,6 +45,8 @@ static void rebalance_wheel(memcached_st *ptr)
 
     ptr->wheel[x]= y;
   }
+
+  return MEMCACHED_SUCCESS;
 }
 
 static int compare_servers(const void *p1, const void *p2)
@@ -65,7 +83,7 @@ memcached_return run_distribution(memcached_st *ptr)
   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
     return update_continuum(ptr);
   case MEMCACHED_DISTRIBUTION_CONSISTENT_WHEEL:
-    rebalance_wheel(ptr);
+    return rebalance_wheel(ptr);
     break;
   case MEMCACHED_DISTRIBUTION_MODULA:
     if (ptr->flags & MEM_USE_SORT_HOSTS)
diff --git a/tests/function.c b/tests/function.c
index a08e1eaa..dc4e6e9a 100644
--- a/tests/function.c
+++ b/tests/function.c
@@ -2458,6 +2458,23 @@ memcached_return set_memory_alloc(memcached_st *memc)
   return MEMCACHED_SUCCESS;
 }
 
+memcached_return enable_wheel(memcached_st *memc)
+{
+  memcached_server_distribution value= MEMCACHED_DISTRIBUTION_CONSISTENT_WHEEL;
+  memcached_hash hash;
+  memcached_behavior_set(memc, MEMCACHED_BEHAVIOR_DISTRIBUTION, value);
+  pre_hsieh(memc);
+
+  value= (memcached_server_distribution)memcached_behavior_get(memc, MEMCACHED_BEHAVIOR_DISTRIBUTION);
+  assert(value == MEMCACHED_DISTRIBUTION_CONSISTENT_WHEEL);
+
+  hash= (memcached_hash)memcached_behavior_get(memc, MEMCACHED_BEHAVIOR_HASH);
+  assert(hash == MEMCACHED_HASH_HSIEH);
+
+
+  return MEMCACHED_SUCCESS;
+}
+
 memcached_return enable_consistent(memcached_st *memc)
 {
   memcached_server_distribution value= MEMCACHED_DISTRIBUTION_CONSISTENT;
@@ -2689,6 +2706,7 @@ collection_st collection[] ={
   {"poll_timeout", poll_timeout, 0, tests},
   {"gets", enable_cas, 0, tests},
   {"consistent", enable_consistent, 0, tests},
+  {"wheel", enable_wheel, 0, tests},
   {"memory_allocators", set_memory_alloc, 0, tests},
 //  {"udp", pre_udp, 0, tests},
   {"version_1_2_3", check_for_1_2_3, 0, version_1_2_3},