Messages in this thread |  | | | Date | Thu, 29 Apr 2004 11:32:26 -0700 | | From | William Lee Irwin III <> | | Subject | Re: ~500 megs cached yet 2.6.5 goes into swap hell |
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On Thu, Apr 29, 2004 at 11:05:42AM -0700, Brett E. wrote: > Anyone know what I should believe? Sar's pgpgin/s and pgpgout/s tell me > that it is paging in/out from/to disk. Yet pswpin/s and pswpout/s are > both 0. Swapping and paging are the same thing I believe. pgpgin/out > refer to paging, pswpin/out refer to swapping. So I for one am confused. > I guess I could dig through the source but I figured someone might have > encountered this disrepency in the past.
Both are to be believed. They merely describe different things.
Pagein/pageout are counts of VM-initiated IO, regardless of whether this IO is done on filesystem-backed pages or swap-backed pages. Pagein and pageout are used more generally to describe VM-initiated IO and don't exclusively refer to swap IO, but also include IO to filesystems to/from filesystem-backed memory.
Swapin/swapout are counts of swap IO only, and are considered to apply only to IO done to swap files/devices to/from swap-backed anonymous memory.
Pagein/pageout are both proper and necessary to have. In fact, you were requesting that filesystem IO be done preferentially to swap IO, and the pagein/pageout indicators showing IO while swapin/swapout indicators show none mean you are getting exactly what you asked for.
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