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List:       freebsd-hackers
Subject:    Re: Clists limited to 1024 bytes?
From:       Simon Shapiro <Shimon () i-Connect ! Net>
Date:       1997-06-30 17:21:11
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Hi Bruce Evans;  On 29-Jun-97 you wrote: 

...

> Logging the error may delay completion for a long time.  Disks shouldn't
> be very sensitive to this, but...  Try turning of log() and printf().
> I usually do this by temporarily replacing the first byte in the routine
> by 0xc3 (ret).

[ Backwards ]  The `ret' trick is as old as I am.  wonder how well it (C3) 
will work on an Alpha :-)  BTW, this is an 8080 opcode, methinks..

I think the problem we suffer from is not necessarily due to delays but
something else.  What we see is either completions reported by calling
 scsi_done being lost, or something that scsi_done does when called getting
lost.  The symptom is; A calling user process (dd, cpio, compilation, etc.)
simply blocks indefinitely in biowait.

This is manifested by having a PPP session running.  Load is not very
important.  Without PPP I can bring the system to LA of 120 or so, without
problem.  With PPP connected, all you have to do is receive email while
running make world.  Somewhere in the middle, things wil start dying.

This is much mode so on a P6 than a P5.

Simon

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