Messages in this thread | | | Subject | Re: Swap performance statistics in 2.6 -- which /proc file has it? | From | Stephen Satchell <> | Date | Tue, 09 Dec 2003 17:28:51 -0800 |
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On Tue, 2003-12-09 at 11:53, Dominik Kubla wrote: > Richard B. Johnson wrote: > > If you need statistics v.s. time, you need to write an application > > that samples things at some fixed interval. In a previous life, > > I requested that "nr_free_pages()" be accessible from user-space, > > probably via /proc. That's all you need. Maybe that could be > > added now? In any event, samping free pages at some fixed-time > > interval should give you all the information you need. > > vmstat -a > sar -B > sar -r > > O'Reilly's "System Performance Tuning" might make for an interesting read, > especially pages 110ff (also its Linux informations are a bit out of date).
How does sampling free pages give you an accurate measurement of swap activity? If I look at the free-page count at one-minute intervals, the system can, and WILL, inhale and exhale pages at a frightening clip, and there is no way I can see that sampling free-page count in a low-overhead way will do the trick.
How does vmstat disk-swap activity? Looking at the source for vmstat in procps-2.0.11 I see how they do it for 2.4 kernels, but the part for 2.5 kernels doesn't seem to try to pick up swap statistics at all -- because there are none to get?
(signed) Puzzled.
(Why does this whole discussion remind me of the Firesign Theatre album _I Think We're All Bozos On This Bus_, and the question that Ah Clem asked: "Why does the porridge-bird lay his eggs in the air?")
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