Thread View: comp.os.linux.development.system
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Started by Steve Wyles
Thu, 09 Feb 1995 17:17
Disk activity blocking serial interrupts (Linux 1.1.81 -> 1.1.90)
Author: Steve Wyles
Date: Thu, 09 Feb 1995 17:17
Date: Thu, 09 Feb 1995 17:17
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Having recently upgraded my kernel version from 1.1.52 to 1.1.81 and
then applying patches when available to 1.1.90, I'm experiencing some weird
behaviour with serial port io.
System configuration
~~~~~~~~~~~~~~~~~~~~
Machine: Hewlett Packard 386/25N, 8Mb Ram, Math Co-processor
Disks: Internal Quantum PD170 IDE, External CDC 94161-9 SCSI on AHA1510
host adaptor.
Serial Ports: 2 x 16450 Uarts
Kernel: 1.1.90
Symptoms
~~~~~~~~
The symptoms show up as a reduction in serial io speed when there
is any disk activity either to the internal IDE or external SCSI drive,
this manifests as a significant retrying of TCP/IP packets over my dial-up
slip link to my provider and also to a local machine using PPP under KA9Q.
Both serial ports are currently running at 38400 and even reducing them
down to as low as 4800 doesn't seem to cure the problem. Incidently even
at 38400 there are no reports of serial overruns in the syslog and have
successfully used this configuration under both 1.0.9 and 1.1.52 with no
loss in throughput.
Having quickly looked at the kernel source it appears the
interrupt processing has changed to a queued method for most devices
(certainly serial & tty) but apparently not for disk related activity.
Could it be that this is the cause of the problem and has anybody else
noticed these symptoms?
Forever living in hope :-)
Steve
--
(=====)-----------------------------------------------------(=====)
| / | Steve Wyles steve@g6vju.demon.co.uk | \ |
| / | Bracknell, Berkshire, UK +44 (0)1344 423102 | \ |
[_____]-----------------------------------------------------[_____]
Re: Disk activity blocking serial interrupts (Linux 1.1.81 -> 1.1.90)
Author: Brandon S. Allbery
Date: Thu, 09 Feb 1995 23:06
Date: Thu, 09 Feb 1995 23:06
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Also sprach steve@g6vju.demon.co.uk (Steve Wyles) (<D3qtDy.Hu@g6vju.demon.co.uk>): +--------------- | The symptoms show up as a reduction in serial io speed when there | is any disk activity either to the internal IDE or external SCSI drive, | this manifests as a significant retrying of TCP/IP packets over my dial-up | slip link to my provider and also to a local machine using PPP under KA9Q. +------------->8 It's rather worse than that: since somewhere around 1.1.70 disk activity preempts *everything* (the system just plain *stops* until the disk I/O completes). Given that this coincided with the appearance of spurious errors from by BT445C, I suspect it also interacts rather badly with VLB disk controllers. ++Brandon -- Brandon S. Allbery KF8NH [44.70.248.67] bsa@kf8nh.wariat.org Linux development: iBCS2, JNOS, MH MLS '96 (I do hope!) ~\U
Re: Disk activity blocking serial interrupts (Linux 1.1.81 -> 1.1.90)
Author: Yann Dupont
Date: Fri, 10 Feb 1995 07:52
Date: Fri, 10 Feb 1995 07:52
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Brandon S. Allbery (bsa@kf8nh.wariat.org) wrote:
: Also sprach steve@g6vju.demon.co.uk (Steve Wyles) (<D3qtDy.Hu@g6vju.demon.co.uk>):
: +---------------
: | The symptoms show up as a reduction in serial io speed when there
: | is any disk activity either to the internal IDE or external SCSI drive,
: | this manifests as a significant retrying of TCP/IP packets over my dial-up
: | slip link to my provider and also to a local machine using PPP under KA9Q.
: +------------->8
: It's rather worse than that: since somewhere around 1.1.70 disk activity
: preempts *everything* (the system just plain *stops* until the disk I/O
: completes). Given that this coincided with the appearance of spurious errors
: from by BT445C, I suspect it also interacts rather badly with VLB disk
: controllers.
Well, I have a BT445S (older), but haven't seen problems with it so far...
currently using 1.1.90. (Config : 486 Dx2/66 + VLB )
Anyway, i'm also victim, on my other computer (a 386 Sx40) of troubles
with serial I/O , since 1.1.8? ... Returning to 1.1.72 cured the problem.
I'm not sure this a to do with disks. On this computer I have a 120 Mb Ide
& 2 SCSI disks, connected to a future Domain Tmc 850 (Yes, the old one, 8bits)
I have 2 28.8 Vfast modems, one external on & 16450, the other internal
(whith a 16550A built in)
When I Send on the external, and receive on the internal, everything is OK,
full speed... And, of course, as i send & receive on the same computer,
*THERE IS* disk activity...
When I Receive on the external, and send on the internal, I've got lots of
errors. Typical, with Zmodem : CRC error every 5 Kb
Even with lower speed (14.4, 9600 ..) I have the same problem.
As I Said earlier, with 1.1.72 it's ok...
--
Yann Dupont - Universite de Nantes : dupont@unantes.univ-nantes.fr
- home, sweet home (cafard naum BBS) : myst@cafard.freenix.fr
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