Weighted Least-Connection Scheduling - Revision history

Wensong: /* Introduction */

2006-12-17T04:48:09Z

‎Introduction

Wensong at 02:08, 17 December 2006

2006-12-17T02:08:24Z

Wensong: Description of Weighted Least-Connection Scheduling moved to Weighted Least-Connection Scheduling: later we can add more things including description

2006-12-17T02:03:45Z

Description of Weighted Least-Connection Scheduling moved to Weighted Least-Connection Scheduling: later we can add more things including description

Wensong at 09:33, 6 August 2005

2005-08-06T09:33:38Z

Wensong at 02:41, 31 July 2005

2005-07-31T02:41:24Z

Wensong at 10:39, 20 July 2005

2005-07-20T10:39:50Z

New page

The weighted least-connection scheduling is a superset of the least-connection scheduling, in which you can assign a performance weight to each real server. The servers with a higher weight value will receive a larger percentage of live connections at any one time. The Virtual Server Administrator can assign a weight to each real server, and network connections are scheduled to each server in which the percentage of the current number of live connections for each server is a ratio to its weight. The default weight is one.

The weighted least-connections scheduling works as follows:

Supposing there is n real servers, each server i has weight Wi (i=1,..,n), and alive
connections Ci (i=1,..,n), ALL_CONNECTIONS is the sum of Ci (i=1,..,n), the next network
connection will be directed to the server j, in which

(Cj/ALL_CONNECTIONS)/Wj = min { (Ci/ALL_CONNECTIONS)/Wi } (i=1,..,n)

Since the ALL_CONNECTIONS is a constant in this lookup, there is no need to divide Ci by
ALL_CONNECTIONS, it can be optimized as

Cj/Wj = min { Ci/Wi } (i=1,..,n)

The weighted least-connection scheduling algorithm requires additional division than the least-connection. In a hope to minimize the overhead of scheduling when servers have the same processing capacity, both the least-connection scheduling and the weighted least-connection scheduling algorithms are implemented.

[[Category:Job Scheduling Algorithms]]

@@ Line 1: / Line 1: @@
 == Introduction ==
-The weighted least-connection scheduling is a superset of the least-connection scheduling, in which you can assign a performance weight to each real server. The servers with a higher weight value will receive a larger percentage of active connections at any one time. The default server weight is one, and the [[IPVS]] Administrator or monitoring program can assign any weight to real server. In the weighted least-connections scheduling, new network connection is assigned to a server which has the least ratio of the current active connection number to its weight.
+The weighted least-connection scheduling is a superset of the [[Least-Connection Scheduling|least-connection scheduling]], in which you can assign a performance weight to each real server. The servers with a higher weight value will receive a larger percentage of active connections at any one time. The default server weight is one, and the [[IPVS]] Administrator or monitoring program can assign any weight to real server. In the weighted least-connections scheduling, new network connection is assigned to a server which has the least ratio of the current active connection number to its weight.
 == Algorithm ==

@@ Line 1: / Line 1: @@
 The weighted least-connection scheduling is a superset of the least-connection scheduling, in which you can assign a performance weight to each real server. The servers with a higher weight value will receive a larger percentage of active connections at any one time. The default server weight is one, and the [[IPVS]] Administrator or monitoring program can assign any weight to real server. In the weighted least-connections scheduling, new network connection is assigned to a server which has the least ratio of the current active connection number to its weight.
 The weighted least-connection scheduling works as follows:
@@ Line 32: / Line 36: @@
   return NULL;
-The weighted least-connection scheduling algorithm requires additional division than the least-connection. In a hope to minimize the overhead of scheduling when servers have the same processing capacity, both the least-connection scheduling and the weighted least-connection scheduling algorithms are implemented.
+The weighted least-connection scheduling algorithm requires additional division than the [[Least-Connection Scheduling|least-connection scheduling]]. In a hope to minimize the overhead of scheduling when servers have the same processing capacity, both the [[Least-Connection Scheduling|least-connection scheduling]] and the weighted least-connection scheduling algorithms are implemented.
 [[Category:Job Scheduling Algorithms]]

@@ Line 15: / Line 15: @@
     C(Sm) / W(Sm) = min { C(Si) / W(Si)}  (i=0, 1, . , n-1), where W(Si) isn't zero
-  Since division operation needs much more than multiply operation, and Linux does
+  Since division operation eats much more CPU cycles than multiply operation, and Linux
-  not allow float mode inside the kernel, the condition C(Sm)/W(Sm) > C(Si)/W(Si)
+  does not allow float mode inside the kernel, the condition C(Sm)/W(Sm) > C(Si)/W(Si)
   can be optimized as C(Sm)*W(Si) > C(Si)*W(Sm). The scheduling should guarantee
   that a server will not be scheduled when its weight is zero. Therefore, the pseudo

← Older revision	Revision as of 02:03, 17 December 2006
(No difference)

@@ Line 1: / Line 1: @@
-The weighted least-connection scheduling is a superset of the least-connection scheduling, in which you can assign a performance weight to each real server. The servers with a higher weight value will receive a larger percentage of live connections at any one time. The Virtual Server Administrator can assign a weight to each real server, and network connections are scheduled to each server in which the percentage of the current number of live connections for each server is a ratio to its weight. The default weight is one.
+The weighted least-connection scheduling is a superset of the least-connection scheduling, in which you can assign a performance weight to each real server. The servers with a higher weight value will receive a larger percentage of active connections at any one time. The default server weight is one, and the [[IPVS]] Administrator or monitoring program can assign any weight to real server. In the weighted least-connections scheduling, new network connection is assigned to a server which has the least ratio of the current active connection number to its weight.
-The weighted least-connections scheduling works as follows:
+The weighted least-connection scheduling works as follows:
-  Supposing there is n real servers, each server i has weight Wi (i=1,..,n), and alive
+  Supposing there is a server set S = {S0, S1, ..., Sn-1},
-  connections Ci (i=1,..,n), ALL_CONNECTIONS is the sum of Ci (i=1,..,n), the next network
+  W(Si) is the weight of server Si;
- connection will be directed to the server j, in which
+ C(Si) is the current connection number of server Si;
-  (Cj/ALL_CONNECTIONS)/Wj = min { (Ci/ALL_CONNECTIONS)/Wi } (i=1,..,n)
+  The new connection is assigned to the server j, in which
-  Since the ALL_CONNECTIONS is a constant in this lookup, there is no need to divide Ci by
+  Since division operation needs much more than multiply operation, and Linux does
-  ALL_CONNECTIONS, it can be optimized as
+  not allow float mode inside the kernel, the condition C(Sm)/W(Sm) > C(Si)/W(Si)
-  Cj/Wj = min { Ci/Wi } (i=1,..,n)
+  for (m = 0; m < n; m++) {
 The weighted least-connection scheduling algorithm requires additional division than the least-connection. In a hope to minimize the overhead of scheduling when servers have the same processing capacity, both the least-connection scheduling and the weighted least-connection scheduling algorithms are implemented.
 [[Category:Job Scheduling Algorithms]]