Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Christoph Lameter]

Given the minimal nature of the patch I would suggest that it become part
of 2.4.10 or 11

On 7 Sep 2001, Robert Love wrote:

> As for integrating into the kernel, there has been talk of preemption
> becoming standard for 2.5.  This is one reason why I keep the patches up
> to date.  When 2.5 starts, I will have a working patch that has seen
> some use and hopefully generated some benchmarks and discussions, and I
> can send a diff off to Linus.  We shall see.

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Robert Love]

On Fri, 2001-09-07 at 00:36, Christoph Lameter wrote:
> Given the minimal nature of the patch I would suggest that it become part
> of 2.4.10 or 11

Are you kidding?  We will be lucky to see this in during 2.5.

Its a pretty big change.  It makes the Linux kernel preemptible.   This
is a fairly big move, one I don't think any of the major Unices have
done.  The only reason the patch is not _huge_ is because the Linux
kernel is already setup for concurrency of this nature -- it does SMP.

I suggest you read
http://www.linuxdevices.com/articles/AT4185744181.html
http://www.linuxdevices.com/articles/AT5152980814.html
http://kpreempt.sourceforge.net

and my previous threads on this issue, for more informaiton.

-- 
Robert M. Love
rml at ufl.edu
rml at tech9.net

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Daniel Phillips]

On September 7, 2001 06:45 am, Robert Love wrote:
> On Fri, 2001-09-07 at 00:36, Christoph Lameter wrote:
> > Given the minimal nature of the patch I would suggest that it become part
> > of 2.4.10 or 11
> 
> Are you kidding?  We will be lucky to see this in during 2.5.
> Its a pretty big change.  It makes the Linux kernel preemptible.

CONFIG_PREEMPT

> This is a fairly big move, one I don't think any of the major Unices have
> done.

The other Unices are at least evenly split, or mostly preemptible.
Typically, a more complex strategy is used where spinlocks can sleep
after a few spins.  This patch is very conservative in that regard,
it basically just uses the structure we already have, SMP spinlocks.

> The only reason the patch is not _huge_ is because the Linux
> kernel is already setup for concurrency of this nature -- it does SMP.
> 
> I suggest you read
> http://www.linuxdevices.com/articles/AT4185744181.html
> http://www.linuxdevices.com/articles/AT5152980814.html
> http://kpreempt.sourceforge.net
> 
> and my previous threads on this issue, for more informaiton.

Hmm, how did you read those and come to such a different conclusion?

--
Daniel

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Robert Love]

On Fri, 2001-09-07 at 01:19, Daniel Phillips wrote:
> On September 7, 2001 06:45 am, Robert Love wrote:
> > On Fri, 2001-09-07 at 00:36, Christoph Lameter wrote:
> > > Given the minimal nature of the patch I would suggest that it become part
> > > of 2.4.10 or 11
> > 
> > Are you kidding?  We will be lucky to see this in during 2.5.
> > Its a pretty big change.  It makes the Linux kernel preemptible.
> 
> CONFIG_PREEMPT

and... ?

> > This is a fairly big move, one I don't think any of the major Unices have
> > done.
> 
> The other Unices are at least evenly split, or mostly preemptible.
> Typically, a more complex strategy is used where spinlocks can sleep
> after a few spins.  This patch is very conservative in that regard,
> it basically just uses the structure we already have, SMP spinlocks.

I did not know other Unices were (in general) preemptible.  Solaris is?
The only one I thought was preemptible was Irix.

Anyhow, you are right about the simplistic approach we take.  There are
a few alternatives: mixing mutexes and shorter locks, priority-bearing
semaphores, changing the way the preemption count works, etc.

> > The only reason the patch is not _huge_ is because the Linux
> > kernel is already setup for concurrency of this nature -- it does SMP.
> > 
> > I suggest you read
> > http://www.linuxdevices.com/articles/AT4185744181.html
> > http://www.linuxdevices.com/articles/AT5152980814.html
> > http://kpreempt.sourceforge.net
> > 
> > and my previous threads on this issue, for more informaiton.
> 
> Hmm, how did you read those and come to such a different conclusion?

What different conclusion? What are you even arguing with me about? 

Do you think I am against a preemptible kernel?  I _posted_ the damn
patch, of course I am not.

I probably agree with whatever you are thinking.

-- 
Robert M. Love
rml at ufl.edu
rml at tech9.net

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Daniel Phillips]

On September 7, 2001 07:20 am, Robert Love wrote:
> On Fri, 2001-09-07 at 01:19, Daniel Phillips wrote:
> > On September 7, 2001 06:45 am, Robert Love wrote:
> > > On Fri, 2001-09-07 at 00:36, Christoph Lameter wrote:
> > > > Given the minimal nature of the patch I would suggest that it become part
> > > > of 2.4.10 or 11
> > > 
> > > Are you kidding?  We will be lucky to see this in during 2.5.
> > > Its a pretty big change.  It makes the Linux kernel preemptible.
> > 
> > CONFIG_PREEMPT
> 
> and... ?

Sorry, I thought that was self-evident.  It's not a change, it's an option.

> What different conclusion? What are you even arguing with me about? 
> 
> Do you think I am against a preemptible kernel?  I _posted_ the damn
> patch, of course I am not.
> 
> I probably agree with whatever you are thinking.

Yes, violent agreement.  OK, I disagree with your assessment that it's 
a huge change.  Big in effect yes, but not in structural impact.

And you're right, I did think you were arguing against your own patch.

--
Daniel

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Robert Love]

On Fri, 2001-09-07 at 01:35, Daniel Phillips wrote:
> Sorry, I thought that was self-evident.  It's not a change, it's an option.

Oh, yes.  It is completely an option -- although I would like to see it
be the norm :)

> Yes, violent agreement.  OK, I disagree with your assessment that it's 
> a huge change.  Big in effect yes, but not in structural impact.

Right, actually I agree with you.  That was my point about using SMP
lock points.  Since it uses the existing structure for SMP concurrency,
the patch is small -- but its effects are pretty large.  Its a fairly
big deal.

> And you're right, I did think you were arguing against your own patch.

No, but I had to take that approach as it was suggested the patch be
merged for 2.4.10!

I am glad you take a pro side to the preemption issue.  Hopefully I can
get some continued support and see some work towards inclusion in 2.5. 
Any help is appreciated.

Sorry for the confusion.

-- 
Robert M. Love
rml at ufl.edu
rml at tech9.net

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[safemode]

I'm using the 2.4.9-ac9 preempt patch to test things out.  Everything is fine 
and stable except it seems that sudden and rapid network accesses cause tiny 
"pops" in the soundcard that didn't occur before the patch.  This is not 
increased system load or anything so the audio isn't skipping due to that. 
It has only happened so far when grabbing many tiny files in rapid succession 
(note. only at 70K/s).  Weird.

Re: Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Chris Ricker]

On 7 Sep 2001, Robert Love wrote:

> On Fri, 2001-09-07 at 01:19, Daniel Phillips wrote:
> > The other Unices are at least evenly split, or mostly preemptible.
> > Typically, a more complex strategy is used where spinlocks can sleep
> > after a few spins.  This patch is very conservative in that regard,
> > it basically just uses the structure we already have, SMP spinlocks.
> 
> I did not know other Unices were (in general) preemptible.  Solaris is?
> The only one I thought was preemptible was Irix.

Solaris is, and has been since good ol' Solaris 2.0.  So's AIX and even more
obscure things like DG/UX.  I'd think all SysVR4 derivatives have to be, by
virtue of the SysV schedular (threads have priorities from 0 to 159; system
threads run from 60 to 99, so the schedular must be able to preempt system 
threads for the real-time threads from 100 to 159).

later,
chris

-- 
Chris Ricker                                               kaboom@gatech.edu
                                                          chris@gurulabs.com

Linux Preemptive patch success 2.4.10-pre4 + lots of other patches

[Christoph Lameter]

I was able to run it on my laptop (compay presario) with 2.4.10-pre4 plus
kernel preemption patch plus

acpi development patches (battery status still unavailable though sigh).
tulip-0.92wax (Support for CONEXTANT onboard Ethernet)
wlan-ng 0.1.8-pre13 + airsnort patches (for SMC WiFi Card)

Seems to work very well.... Wish all the above stuff would be making it
into the kernel soon.. I keep having to patch up the kernels.

Amazing support for hardware considering I saw no support for the ACPI
stuff and the onboard ethernet when I bought the laptop....