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Date: Mon, 20 Oct 2008 14:50:19 -0700
From: Andrew Sharp <andy.sharp@onstor.com>
To: "Maxim Kozlovsky" <maxim.kozlovsky@onstor.com>
Cc: "Bill Fisher" <bfisher@onstor.com>
Subject: Re: ACPU/NCPU Linux Proposal and Task List; Take 2
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On Mon, 20 Oct 2008 12:07:14 -0700 "Maxim Kozlovsky"
<maxim.kozlovsky@onstor.com> wrote:

> 
> 
> >-----Original Message-----
> >From: Andy Sharp
> >Sent: Friday, October 17, 2008 6:46 PM
> >To: Maxim Kozlovsky
> >Cc: Bill Fisher
> >Subject: Re: ACPU/NCPU Linux Proposal and Task List; Take 2
> >
> >On Fri, 17 Oct 2008 11:57:38 -0700 "Maxim Kozlovsky"
> ><maxim.kozlovsky@onstor.com> wrote:
> >
> >From now on, the "NCPU kernel" shall simply be referred to as
> >"TUXRX". Please modify this document to reflect this.
> [MK] Andy you suck at inventing acronyms. Try something else. 

Your jealousy is showing.  It's definitely the BAE.

> >We can easily use sockets/network pipes for this.  But we will want
> >NFS client all over the place for development.  NFS root filesystem,
> >etc.
> [MK] You can't use socket/pipes for writing tcpdump from NCPU. Where
> you are going to terminate the other end of the pipe?

Somewhere out on the "cloud."  But seriously, the NFS thing is better,
so nm.

> >I'm not seeing why we would need any functionality similar to the
> >"passive crash" thing you describe, but maybe I'm not fully getting
> >what that is.  Are you saying you want the ACPU thread(s) to "stop"
> >when an FP core crashes?  We can do the equivalent of that.
> [MK] The objective is to panic the TXRX when FP crashes/panics, and to
> panic the FP when the TXRX crashes/panics. 

Still not getting it completely.  I assume everone else is, so I'll
leave it alone.

> >
> >I'm also not seeing why we would need interrupts.  Is polling not
> >good enough for the kernel?
> [MK] 
> You will need the interrupts if you are going to run any user space
> stuff on NCPU.

Well, yeah, we will have interrupts in general, but that doesn't mean
everything has to use interrupts.

> >> Profiler support - gprof and sibyte profilers will need to be
> >> supported for NCPU and ACPU.
> >
> >Hmm.  Are you sure top(1) won't be good enough?  There are various
> >kernel profiling "subsystems" that we can employ.
> [MK] 
> No top is not good enough.  

I was joking.

> >> Watchdog support - I assume this will have to change since Linux
> >> has its own watchdog driver. The ACPU should be able to
> >> start/stop/kick its watchdog.
> >
> >Well there's the Sibyte WD driver I wrote as well as the softdog
> >driver.
> [MK] 
> Does it work for multiple cores? It should also export the interface
> for ACPU.

Absolutely works for multiple cores, and there is two hardware WDs per
pair of cores on the 1480: one is kept on the kernel side for kernel
use, the other is exported to userspace.  That should be good enough
since the plan is to use 3 cores in SMP configuration and one core
pinned to the ACPU task, or similar.

> >> >-----Original Message-----
> >> >From: Bill Fisher
> >> >Sent: Thursday, October 16, 2008 5:52 PM
> >> >To: Andy Sharp; Maxim Kozlovsky
> >> >Cc: Bill Fisher
> >> >Subject: ACPU/NCPU Linux Proposal and Task List; Take 2
> >> >
> >> >Guys:
> >> >
> >> >Attached is take 2 of the proposal. I have re-ordered the tasks
> >> >as per Max's suggestion and incorporated the changes as
> >> >per his review comments.
> >> >
> >> >As before, let me know what I am missing or have
> >> >gotten wrong.
> >> >
> >> >Thanks,
> >> >
> >> >-- Bill
> >>
