swap pager:indefinite wait buffer: message out of vm.c

Mark Terribile materribile at yahoo.com
Wed Dec 1 23:35:54 UTC 2010


Would some kind soul please tell me the meaning of a message coming
from vm.c (FreeBSD 7.2):
"swap pager: indefinite wait buffer: bufobj: 0, blkno: 2, size: 4096"

This message occurs after a return from an msleep whose last args are PSWP,
"swread", and HZ*20 .

When it occurs, some interactive program is locked up.  It recovers
sometime later.

My best guess is that this is a complaint that swap or paging I/O has been
excessively delayed.  It is occurring while I am running disk-to-disk
transfers that have deep buffering.  Think mbuf(1), but it's my own code,
testing some algorithms.  I speculate that if the disk queuing/head movement optimization doesn't let the heads move off the file system
where the file resides (and I only see this with large, single files)
then this problem might result.  But that is a guess, and speculation.

Does anyone know if this can occur under later versions of FreeBSD?

Thank you for your help.

    Mark Terribile
    materribile at yahoo.com


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