> >Hello Justin, hello Gerard
> >
> >I am looking currently for reasons for bad behaviour of aic7xxx
driver
> >in an shared interrupt setup and general not-nice behaviour of the
> >driver regarding multi-tasking environment.
>
> Can you be more specific?
Yes, of course :-)
What I am seeing over here is that aic7xxx is _significantly_ slower
than symbios _in the exact same context_. I refused to use the "new"
driver as long as possible because I had (right from the first test)
the "feeling" that it hurts the machine overall performance in some
way, meaning the box seems _slow_ and less responsive than it was with
the old aic driver. When I directly compared it with symbios (LSI
Logic hardware sold from Tekram) I additionaly found out, that it
seems to hurt the interrupt performance of a network card sharing its
interrupt with the aic which again does not happen with symbios. I
have already seen such behaviour before, on merely every driver I
formerly wrote for shared interrupt systems I had to fill in code that
_prevents_ lockout of other interrupt users due to indefinitely
walking through the own code in high load situation.
But, of course, you _know_ this. Nobody writes a driver like new
aic7xxx _and_ doesn't know :-)
My guess is that this knowledge made you enter the comment I ripped
from your code about using bottom half handler instead of dealing with
workload in a hardware interrupt. Again, I have to no extent read your
code completely or the like. I simply tried to find the hardware
interrupt routine and look if it does significant eli (EverLasting
Interrupt ;-) stuff - and I found your comment.
Can you re-comment from todays point of view?
> >This is nice. I cannot read the complete code around it (it is
derived
> >from aic7xxx_linux.c) but if I understand the naming and comments
> >correct, some workload is done inside the hardware interrupt (which
> >shouldn't), which would very much match my tests showing bad
overall
> >performance behaviour. Obviously this code is old (read the
comment)
> >and needs reworking.
> >Comments?
>
> I won't comment on whether deferring this work until outside of
> an interrupt context would help your "problem" until I understand
> what you are complaining about. 8-)
In a nutshell:
a) long lasting interrupt workloads prevent normal process activity
(creating latency and sticky behaviour)
b) long lasting interrupt workloads play bad on other interrupt users
(e.g. on the same shared interrupt)
I can see _both_ comparing aic with symbios.
Regards,
Stephan
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This archive was generated by hypermail 2b29 : Wed Nov 07 2001 - 21:00:22 EST