Subject: system looping on I/O
To: None <>
From: Manuel Bouyer <>
List: current-users
Date: 11/14/2001 14:54:09
for a long time (since about end of july) my sparc IPX dies under heavy I/O
load (such as a sup -o). I/O seems blocked and the disk keep trashing.
I suspect that the same request is sent to the disk again and again,
maybe the VM trying to flush the same dirty page(s) to disk.
Running processes keep running until they try a disk access.
This is not the usual out of swap problem, there is no big process and plenty
of free swap when this happens.

This machine has 2 disks:
scsibus0: waiting 2 seconds for devices to settle...
sd1 at scsibus0 target 1 lun 0: <IMPRIMIS, 94601-15, 4614> SCSI1 0/direct fixed
sd1: 1001 MB, 1931 cyl, 15 head, 70 sec, 512 bytes/sect x 2050995 sectors
sd1: async, 8-bit transfers
sd0 at scsibus0 target 3 lun 0: <CONNER, CP30200  SUN0207, 4544> SCSI2 0/direct fixed
sd0: 203 MB, 2123 cyl, 4 head, 49 sec, 512 bytes/sect x 416108 sectors
sd0: sync (200.0ns offset 15), 8-bit (5.000MB/s) transfers

System is on sd0, swap and sources on sd1. sd1 is really slow, maybe this is
what triggers the problem (race condition somewhere ?).

Anyone else seen this ?

Manuel Bouyer, LIP6, Universite Paris VI.