royong
26-04-2008, 16:59
What exactly does the server load reading from the "top" command actually mean? Here's what I think is worth a read.
The load average numbers give the average number of jobs in the run queue over the last 1, 5, and 15 minutes. (These three time periods may vary from one vendor's Unix system to another, but are usually 1, 5 and 15 minutes.) In other words, the n-minute load average is the number of processes competing for the attention of the CPU(s) at any moment, averaged over n minutes.
The lowest possible load average is zero, the highest unlimited, though we rarely see load averages exceeding 20, and even 10 is unusual. A load average of one or two is about typical.
A load average of 0.02 means that there is an average of 0.02 processes in the run queue. This might mean that 98% of the time the processor is doing nothing and the remaining time it has a single process to run; it might mean that 99% of the time the processor is doing nothing and 1% of the time there are two processes doing stuff; it might mean that the processor is idle 99.9% of the time and the remaining 0.1% of the time there are 20 processes doing stuff.
The cpu utilization will always be lower than the load average, but the difference between them depends upon how often two differing processes simultaneously want cpu time.
CPU Load Average
Description:
Determines the typical processing load patterns on your CPU. It is a measure of the amount of work that the CPU is experiencing.
Purpose: Determines if your system is overloaded.
Indicators:
A load value average that is consistently above the efficient load value indicates an overloaded server.
Systems perform best when the load average is less than or equal to the maximum efficient load value, which is the number of CPUs in the system. For single-CPU systems, the load average should be decimal values such as .22, .54, and .99. Although it is normal for the load average to spike over the efficient load value at times, a load average that is consistently above the efficient load value indicates an overloaded server.
Load Average
On a single processor machine, a load of 1 is maximum efficient utilization. Loads more than the number of processors mean the machine is too heavily loaded. Any load numbers in the 2 or 3 range is an indication of excessive CPU use and consequently poor performance. Load average numbers should be in the decimal range, for example; .02 or .53.
Load average is the amount of load that the server's CPU is experiencing. What creates load on a CPU? When a program is run i.e., a search program, a shopping cart program, a request to upload a web site's page to a browser, an email program etc.. When any of the preceding scenarios occur, a load (or demand) is placed on the server's CPU. Some processes are given a higher priority by the CPU i.e., if a server is performing a search and a visiting web surfer happens to request a web page from a site hosted on that same server, then the page upload is given priority over the search. The search will slow down in order to accommodate the page upload.
Relative to page uploads the CPU's load average is not as critical as the pipeline to server. The pipeline is the connection from the server to the backbone provider. Pipelines are designated as 0C3, DS3, T3, T1, etc.. and are an indication of how much data can be transmitted in kilo bytes per second. A heavily loaded CPU will usually be able to out perform the pipeline.
The load average numbers of 0.28, 0.18, 0.22 are reflections of 1, 5 and 15 minute intervals respectively.
Numbers like this "3.30, 1.05, 0.96" are not as much a cause for alarm as numbers like this "2.52, 2.56, 2.51". The second set of numbers show consistent heavy demand on the processor. This consistent heavy load will deny the web pages the priority they need to load quickly. The first set of numbers is indicative of a single process or program (such as a search) performing it's function and will likely end very soon.
The load average numbers give the average number of jobs in the run queue over the last 1, 5, and 15 minutes. (These three time periods may vary from one vendor's Unix system to another, but are usually 1, 5 and 15 minutes.) In other words, the n-minute load average is the number of processes competing for the attention of the CPU(s) at any moment, averaged over n minutes.
The lowest possible load average is zero, the highest unlimited, though we rarely see load averages exceeding 20, and even 10 is unusual. A load average of one or two is about typical.
A load average of 0.02 means that there is an average of 0.02 processes in the run queue. This might mean that 98% of the time the processor is doing nothing and the remaining time it has a single process to run; it might mean that 99% of the time the processor is doing nothing and 1% of the time there are two processes doing stuff; it might mean that the processor is idle 99.9% of the time and the remaining 0.1% of the time there are 20 processes doing stuff.
The cpu utilization will always be lower than the load average, but the difference between them depends upon how often two differing processes simultaneously want cpu time.
CPU Load Average
Description:
Determines the typical processing load patterns on your CPU. It is a measure of the amount of work that the CPU is experiencing.
Purpose: Determines if your system is overloaded.
Indicators:
A load value average that is consistently above the efficient load value indicates an overloaded server.
Systems perform best when the load average is less than or equal to the maximum efficient load value, which is the number of CPUs in the system. For single-CPU systems, the load average should be decimal values such as .22, .54, and .99. Although it is normal for the load average to spike over the efficient load value at times, a load average that is consistently above the efficient load value indicates an overloaded server.
Load Average
On a single processor machine, a load of 1 is maximum efficient utilization. Loads more than the number of processors mean the machine is too heavily loaded. Any load numbers in the 2 or 3 range is an indication of excessive CPU use and consequently poor performance. Load average numbers should be in the decimal range, for example; .02 or .53.
Load average is the amount of load that the server's CPU is experiencing. What creates load on a CPU? When a program is run i.e., a search program, a shopping cart program, a request to upload a web site's page to a browser, an email program etc.. When any of the preceding scenarios occur, a load (or demand) is placed on the server's CPU. Some processes are given a higher priority by the CPU i.e., if a server is performing a search and a visiting web surfer happens to request a web page from a site hosted on that same server, then the page upload is given priority over the search. The search will slow down in order to accommodate the page upload.
Relative to page uploads the CPU's load average is not as critical as the pipeline to server. The pipeline is the connection from the server to the backbone provider. Pipelines are designated as 0C3, DS3, T3, T1, etc.. and are an indication of how much data can be transmitted in kilo bytes per second. A heavily loaded CPU will usually be able to out perform the pipeline.
The load average numbers of 0.28, 0.18, 0.22 are reflections of 1, 5 and 15 minute intervals respectively.
Numbers like this "3.30, 1.05, 0.96" are not as much a cause for alarm as numbers like this "2.52, 2.56, 2.51". The second set of numbers show consistent heavy demand on the processor. This consistent heavy load will deny the web pages the priority they need to load quickly. The first set of numbers is indicative of a single process or program (such as a search) performing it's function and will likely end very soon.