In looking at some load issues on our servers we have starting recording some cn=Monitor counters for analysis. In particular we would like to understand what cn=Backload,cn=Threads,cn=Monitor contains. On our servers we have threads set to 8 and we have seen maximum backload values of 56. Does this means there are 56 connections waiting for an execution thread?
Bill
+-------------------------------------------------------- | Bill MacAllister whm@stanford.edu | Systems Software Programmer, ITS Unix Systems, Stanford University
Bill MacAllister writes:
In looking at some load issues on our servers we have starting recording some cn=Monitor counters for analysis. In particular we would like to understand what cn=Backload,cn=Threads,cn=Monitor contains. On our servers we have threads set to 8 and we have seen maximum backload values of 56. Does this means there are 56 connections waiting for an execution thread?
Someone else could give a better answer but...
No, it's the number of unfinished tasks submitted to the thread pool. Each LDAP operation is submitted as a separate task - i.e. a C function call to be performed. With your numbers, 8 or fewer are active and the remaining 48 are waiting for a thread to pick them up and run them.
Note that some other tasks are also submitted to the thread pool, I don't remember quite which ones. Listening for new connections, reading from and closing a connection, depending on how slapd is compiled. "Run queue" tasks, which I don't remember what are. Replication, maybe.
Hallvard B Furuseth wrote:
Bill MacAllister writes:
In looking at some load issues on our servers we have starting recording some cn=Monitor counters for analysis. In particular we would like to understand what cn=Backload,cn=Threads,cn=Monitor contains. On our servers we have threads set to 8 and we have seen maximum backload values of 56. Does this means there are 56 connections waiting for an execution thread?
Someone else could give a better answer but...
No, it's the number of unfinished tasks submitted to the thread pool. Each LDAP operation is submitted as a separate task - i.e. a C function call to be performed. With your numbers, 8 or fewer are active and the remaining 48 are waiting for a thread to pick them up and run them.
Note that some other tasks are also submitted to the thread pool, I don't remember quite which ones. Listening for new connections, reading from and closing a connection, depending on how slapd is compiled. "Run queue" tasks, which I don't remember what are. Replication, maybe.
Note that in 2.4 a description appears for each thread related monitor entry. The one for backload states "Number of active plus pending threads", which is as much as I could infer from the formula that computes the return value for the call that computes the monitored value.
p.
Ing. Pierangelo Masarati OpenLDAP Core Team
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Bill MacAllister -
Hallvard B Furuseth -
Pierangelo Masarati