Adaptec-2920 eats too much cpu time when reading from the CD-ROM

Adaptec-2920 eats too much cpu time when reading from the CD-ROM

[Florin Iucha]

Hello,

I have recently purchased a Plextor 12x CD-RW and I have attached it to
and Adaptec-2920 SCSI card. The card uses the "Future Domain Corp. TMC-18C30
[36C70]" chip.

The problem I see: when reading from the CD-RW my system becomes very
unresponsive and top reveals 90-95% of the time is spent on "system".
My CPU is AMD K6-III/500MHz with 256 Mb RAM.

When reading the same CD using the IDE DVD-ROM the time spent in system
is 5%. Also when the CD-RW is connected to the Advansys SCSI controller
the CPU usage is also negligible. The Adaptec-2920 uses IRQ 10 and does
not share it with any other board.

I notice an unusual number of interrupts in /proc/interrupts: after the
machine has been up for a couple of hours and I have written three CDs,
the statistics are:
          CPU0       
 0:     638458          XT-PIC  timer
 1:      15325          XT-PIC  keyboard
 2:          0          XT-PIC  cascade
 5:          0          XT-PIC  es1371
 8:          1          XT-PIC  rtc
 9:      17004          XT-PIC  usb-uhci
10:    3032143          XT-PIC  fdomain
11:      58021          XT-PIC  advansys
12:    2995779          XT-PIC  eth0
14:     107542          XT-PIC  ide0
15:       6895          XT-PIC  ide1

When loading the fdomain module I get:
   scsi1: <fdomain> No BIOS; using scsi id 7
   scsi1: <fdomain> TMC-36C70 (PCI bus) chip at 0xdc00 irq 10
   Bad boy: fdomain (at 0xd08b7866) called us without a dev_id!

Is there anything I can try?

Thanks,
florin

-- 

"If it's not broken, let's fix it till it is."

41A9 2BDE 8E11 F1C5 87A6  03EE 34B3 E075 3B90 DFE4

Re: Adaptec-2920 eats too much cpu time when reading from the CD-ROM

[Alan Cox]

> I have recently purchased a Plextor 12x CD-RW and I have attached it to
> and Adaptec-2920 SCSI card. The card uses the "Future Domain Corp. TMC-18C30
> [36C70]" chip.
> 
> The problem I see: when reading from the CD-RW my system becomes very
> unresponsive and top reveals 90-95% of the time is spent on "system".
> My CPU is AMD K6-III/500MHz with 256 Mb RAM.

I'd expect that. The 2920 is pretty old. It has no DMA channel and several
processes it must perform are polled not interrupt driven.

>    scsi1: <fdomain> No BIOS; using scsi id 7
>    scsi1: <fdomain> TMC-36C70 (PCI bus) chip at 0xdc00 irq 10
>    Bad boy: fdomain (at 0xd08b7866) called us without a dev_id!

The Bad boy: line is fixable tho.. This should do it - let me know if it 
makes that one go away.

--- linux.gamma/drivers/scsi/fdomain.h	Sat Nov 17 20:47:53 2001
+++ linux.ac/drivers/scsi/fdomain.h	Thu Dec  6 10:14:51 2001
@@ -43,6 +43,7 @@
 		       abort:          fdomain_16x0_abort,               \
 		       reset:          fdomain_16x0_reset,               \
 		       bios_param:     fdomain_16x0_biosparam,           \
+		       release:        fdomain_16x0_release,		 \
 		       can_queue:      1, 				 \
 		       this_id:        6, 				 \
 		       sg_tablesize:   64, 				 \
--- linux.gamma/drivers/scsi/fdomain.c	Sat Nov 17 20:47:53 2001
+++ linux.ac/drivers/scsi/fdomain.c	Thu Dec  6 10:15:08 2001
@@ -983,7 +983,7 @@
       /* Register the IRQ with the kernel */
 
       retcode = request_irq( interrupt_level,
-			     do_fdomain_16x0_intr, pdev?SA_SHIRQ:0, "fdomain", NULL);
+			     do_fdomain_16x0_intr, pdev?SA_SHIRQ:0, "fdomain", shpnt);
 
       if (retcode < 0) {
 	 if (retcode == -EINVAL) {
@@ -2033,6 +2033,15 @@
    }
    
    return 0;
+}
+
+int fdomain_16x0_release(struct Scsi_Host *shpnt)
+{
+	if (shpnt->irq)
+		free_irq(shpnt->irq, shpnt);
+	if (shpnt->io_port && shpnt->n_io_port)
+		release_region(shpnt->io_port, shpnt->n_io_port);
+
 }
 
 MODULE_LICENSE("GPL");

Re: Adaptec-2920 eats too much cpu time when reading from the CD-ROM

[Florin Iucha]

On Thu, Dec 06, 2001 at 09:28:08AM +0000, Alan Cox wrote:
> > I have recently purchased a Plextor 12x CD-RW and I have attached it to
> > and Adaptec-2920 SCSI card. The card uses the "Future Domain Corp. TMC-18C30
> > [36C70]" chip.
> > 
> > The problem I see: when reading from the CD-RW my system becomes very
> > unresponsive and top reveals 90-95% of the time is spent on "system".
> > My CPU is AMD K6-III/500MHz with 256 Mb RAM.
> 
> I'd expect that. The 2920 is pretty old. It has no DMA channel and several
> processes it must perform are polled not interrupt driven.

There is one interesting thing about it: when I write a CD, I write at 12x
- that means 1800Kb/s, which is comparable with the reading speed of 2400Kb/s.
But when writing, the system CPU usage is about 30%.

What could make the controller eat so much time when reading but not when
writing?

Thanks,
florin

PS. The patch fixes the "bad boy" message.

-- 

"If it's not broken, let's fix it till it is."

41A9 2BDE 8E11 F1C5 87A6  03EE 34B3 E075 3B90 DFE4

Re: Adaptec-2920 eats too much cpu time when reading from the CD-ROM

[Alan Cox]

> There is one interesting thing about it: when I write a CD, I write at 12x
> - that means 1800Kb/s, which is comparable with the reading speed of 2400Kb/s.
> But when writing, the system CPU usage is about 30%.

When you write the scsi layer keeps getting to the point where there are
no commands to issue. When you read its always there waiting for the drive.