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Old 02-21-2009, 02:23 AM   #1
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RedHat As4.0 Performance tuning question


I need documentaions/URLs to determine the performance tuning settings and programs. I know commands like top, vmstat, iostat, sar but Iam unable to dig out the right metrics. Like how much swapping is acceptable & how much should be avoided. Similarly on I/O what numbers indicate performance problems. Also on CPU what how much load is acceptable.

Thanks in advance.
Old 02-22-2009, 06:28 AM   #2
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Those are really subjective.. if the users (or remote systems) don't complain, its fast enough...

Generally I'd say that >10% of swap being used (all the time) may be a problem, but not critical unless it keeps going up.
If swap does keep increasing, then eventually you'll get major slowdown (thrashing) and ultimately, when swap is full, the oomkiller will start killing processes.
Another rough rule of thumb is keep disks no more than 80% full, otherwise any heavier than usual load will fill them up (=> crash) before you get a chance to fix the issue.
For CPU, iirc, if all 3 values are >5 that's a bit high, >10 (consistently) is usually regarded as a bad thing, but keep in mind my first sentence....
Old 02-22-2009, 07:09 AM   #3
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This isn't a particularly well-written article, but it could give you an overview, which should be helpful.


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