Dieter wrote:
AMD64 FreeBSD 7.0 2 GiB main memory
My console says:
login: swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096
swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096
pstat -sk
Device 1K-blocks Used Avail Capacity
/dev/ad6s10 4590208 96 4590112 0%
Wow, using a whole 96K of swap. I don't see any disk related
complaints in dmesg.
Is this something to worry about?
Yes, the system was *trying* to do swap I/O and timing out while doing so.
Kris
Whoops, I forgot to change the subject line after adding the k option
to pstat. Without the k it said 0 used. And this morning it occurs to
me that even if swap used was zero, it could have been trying to *start*
using swap.
Anyway... given this timeout explaination, I'm guessing that page/swap
has to compete with user processes for disk i/o, and thus probably
suffers from the same lack of fair i/o scheduling that user processes
suffer from. E.g. one process doing disk i/o can lock out another
process for at least several minutes, probably indefinitely. :-(
There is a timeout of (from memory) 60 seconds. I've not seen this
timeout exceeded on properly functioning disk hardware (even heavily
loaded), only on broken hardware/controllers, or on I/O devices that are
intrinsically slow for some reason (USB stick, or swapping to a file).
Unless you're doing something truly unspeakable to that disk's load, I'd
look at the hardware.
Kris
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