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performance:linux-performance-tracking [2009-10-09 23:39:46] garrett.plasky |
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| Together all of these figures add up to 100%. Generally you don't need to be concerned with all of these metrics, however there are a few that are very important. Any activity that generates CPU activity will reduce the **id** % and depending on how the load was generated, increase one of the others. In most cases these are either **us** or **wa**. Depending on your hardware, it is normal to see anywhere from 1-100% **us** usage. **wa**, however, should ideally be 0%, or as near to 0% as possible. | Together all of these figures add up to 100%. Generally you don't need to be concerned with all of these metrics, however there are a few that are very important. Any activity that generates CPU activity will reduce the **id** % and depending on how the load was generated, increase one of the others. In most cases these are either **us** or **wa**. Depending on your hardware, it is normal to see anywhere from 1-100% **us** usage. **wa**, however, should ideally be 0%, or as near to 0% as possible. | ||
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| As this value increases, there is more and more CPU time being spent waiting for system I/O to finish (usually harddrive). Values of even as much as 0.5% have been known to cause slowing on older SATA and PATA drives. This number will almost always be >1% when your server is using swap space (more on that later). Next we'll cover how to get more information about what in particular might cause undesirable **wa** percentages. | As this value increases, there is more and more CPU time being spent waiting for system I/O to finish (usually harddrive). Values of even as much as 0.5% have been known to cause slowing on older SATA and PATA drives. This number will almost always be >1% when your server is using swap space (more on that later). Next we'll cover how to get more information about what in particular might cause undesirable **wa** percentages. | ||
