<br><br><div class="gmail_quote">On Mon, Apr 22, 2013 at 5:33 AM, Bert Freudenberg <span dir="ltr"><<a href="mailto:bert@freudenbergs.de" target="_blank">bert@freudenbergs.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br><div style="word-wrap:break-word"><div>Still, you make it sound like this inefficiency is actually preventing the Stack VM from running on the Raspberry Pi? That is hard to believe.</div></div></blockquote><div><br></div>
<div>No, we just use the interval timer. But as I say in a server/multi-user/ffi context the interval timer is problematic.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word"><div><br></div><div><span style="border-collapse:separate;border-spacing:0px;font-size:12px"><div style="font-family:Helvetica">- Bert -</div><br></span></div><div><div>On 2013-04-19, at 05:24, Casey Ransberger <<a href="mailto:casey.obrien.r@gmail.com" target="_blank">casey.obrien.r@gmail.com</a>> wrote:</div>
<br><blockquote type="cite"><div dir="ltr">I had a feeling the actual problem was probably political. The name is also a bit... well. As many children will prefer to avoid the use of profanity while raising their parents, I wonder if I shouldn't start by forking it and calling it the Big Furry Scheduler or something...<div>
<br></div><div>Anyhow this sheds lots of light on things. Thank, Eliot!</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Apr 18, 2013 at 1:29 PM, Eliot Miranda <span dir="ltr"><<a href="mailto:eliot.miranda@gmail.com" target="_blank">eliot.miranda@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <br>Hi Casey,<br><br><div class="gmail_quote">On Thu, Apr 18, 2013 at 5:37 AM, Casey Ransberger <span dir="ltr"><<a href="mailto:casey.obrien.r@gmail.com" target="_blank">casey.obrien.r@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br><div dir="ltr">Totally. I know it isn't going to be a small thing. I'm curious if any of the BSD implementations solve the problem adequately for Cog; I might have something working to study, build tests around, etc. A control group.</div>
</blockquote><div><br></div><div>The technical problem was solved for Linux in 2009 by Con Kolivas with his (excuse the language) <a href="http://en.wikipedia.org/wiki/Brain_Fuck_Scheduler" target="_blank">http://en.wikipedia.org/wiki/Brain_Fuck_Scheduler</a>. The political problem of getting it adopted throughout the linux community so it can be relied upon is an entirely different thing.</div>
<div><br></div><div>Note that once BFS is more widely available I could write a VM that will test thread priorities on startup and use threads if multiple priorities are supported, falling back on the ITIMER if not.</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>
<br></div><div>Either way though, it would be a largish win for the community, given the widespread popularity of Linux. I might be able to find some friends who might like to attack it with me. Etcetera.</div><div>
<br></div><div>I wonder about why the Linux folks haven't dealt with it already. Maybe it hasn't come up. Hopefully it isn't a security thing, that'd be hard to make a case about.</div><div><br>
</div><div>Either way, I haven't figured out where to start looking yet.</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Apr 18, 2013 at 5:23 AM, David T. Lewis <span dir="ltr"><<a href="mailto:lewis@mail.msen.com" target="_blank">lewis@mail.msen.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
I think that Eliot has described the issue in some detail either on<br>
this list, or on his blog <a href="http://www.mirandabanda.org/cogblog/" target="_blank">http://www.mirandabanda.org/cogblog/</a>. Sorry<br>
I don't have any links handy, but reading through the blog is time<br>
well spent in any case :)<br>
<br>
I think you are dealing with a fundamental issue in the pthreads<br>
implementation(s) on Linux, so don't be surprised if it's not just<br>
a simple matter of fixing a bug. The pthreads implementation is more<br>
or less grafted onto the original Unix process model, and operating<br>
systems tend to vary as to whether they support pthreads fully, or<br>
for that matter whether they support a thread model at all.<br>
<br>
Dave<br>
<div><br>
On Thu, Apr 18, 2013 at 05:07:42AM -0700, Casey Ransberger wrote:<br>
><br>
> Well I guess maybe I left a part of the message out. Oops. I'm talking<br>
> about Cog's heart. It needs user-level thread prioritization and apparently<br>
> (GNU/?)Linux lacks this.<br>
><br>
> My guess is it's a kernel issue. But that's an uneducated guess.<br>
><br>
> It became interesting to me because I'm not super happy with the UI<br>
> responsiveness of Squeak trunk under the interpreter and Raspbian on a<br>
> 700MHz Pi (out of box experience isn't overclocked, so I'm targeting that.)<br>
> My thought was to get the stack VM going, but we still have this issue with<br>
> the heartbeat for the stack VM to be able to perform optimally. If I can<br>
> fix the heartbeat (read: pthreads) issue, I can benefit GNU/Linux users of<br>
> the system across the board, both in terms of the (Intel) JIT, and in terms<br>
> of the stack oriented virtual machine which has the awesome Ungar-style<br>
> garbage collection, right? I want the efficient GC eventually anyway. The<br>
> advantages of stack orientation are somewhat beyond my current<br>
> understanding of virtual machines, but I gather that's desirable as well?<br>
> </noob><br>
><br>
> I need to do some tests with Cuis, Spoon, Pharo, and Etoys before I'm going<br>
> to blame any part of the VM about the UI perf I'm seeing, but a faster VM<br>
> is a faster VM anyway. I'd like to make all of the images faster on this<br>
> little gadget, because it's cool, it's popular, and it gives us an approach<br>
> on more than just the third world (not that the third world isn't<br>
> incredibly important, just that if we don't start making better adults<br>
> where people with first world problems are too, I'll end up feeling like<br>
> Rick Moranis in Spaceballs or I'm going to have to relocate to someplace<br>
> where we previously made better adults.)<br>
><br>
> <a href="http://www.youtube.com/watch?v=sen8Tn8CBA4" target="_blank">http://www.youtube.com/watch?v=sen8Tn8CBA4</a><br>
><br>
> I know this isn't really the place to ask, but I thought maybe someone<br>
> might be able to point me at what I'd need to dig into to understand the<br>
> problem we have with the popular Linux implementation of pthreads, because<br>
> when I GOOG that, I get #1 a tutorial on using pthreads, #2 a Wikipedia<br>
> article which speaks abstractly about pthreads, and #3 another tutorial on<br>
> using pthreads. I think I'm trying to figure out what to google for so that<br>
> I can figure out where the problem lives and then look at it to see whether<br>
> or not I can steal its lunch money.<br>
><br>
> Even if I google "linux pthreads" I still get a tutorial on using them as<br>
> the top hit.<br>
><br>
> This is the most directly informative thing I can find:<br>
><br>
> <a href="http://man7.org/linux/man-pages/man7/pthreads.7.html" target="_blank">http://man7.org/linux/man-pages/man7/pthreads.7.html</a><br>
><br>
> Hopefully this explains anything I might have left out of my first message<br>
> on the subject!<br>
><br>
> Casey<br>
><br>
><br>
> On Wed, Apr 17, 2013 at 5:33 AM, David T. Lewis <<a href="mailto:lewis@mail.msen.com" target="_blank">lewis@mail.msen.com</a>> wrote:<br>
><br>
> ><br>
> > On Wed, Apr 17, 2013 at 01:15:45AM -0700, Casey Ransberger wrote:<br>
> > ><br>
> > > I'm assuming the problem is in the kernel, but making assumptions is<br>
> > usually a bad plan, so I'm asking.<br>
> > ><br>
> > > When I look, I find a rather confusing jumble: pthreads exists in<br>
> > different implementations under different operating systems.<br>
> > ><br>
> > > I'd kind of like the heartbeat to work right under Raspbian, because<br>
> > kids are going to use it, and the goal of producing better adults is pretty<br>
> > close to my heart. See also making Squeak faster. (Stack VM.)<br>
> > ><br>
> > > I want to arm myself with as much knowledge about this as possible,<br>
> > because I'm considering just bloody fixing it. If the (GNU/Linux) community<br>
> > has objections, and I'm able to pull off the fix, I can make a patch<br>
> > available to people who want it.<br>
> > ><br>
> > > I'm not confident that I can fix the bug with the knowledge I have now,<br>
> > but I'm confident that I can fix it eventually, if someone else doesn't<br>
> > beat me to the punch.<br>
> > ><br>
> > > Outside of the wiki page, are there any documents/people/mailing lists I<br>
> > should look at to be able to get a good handle on where in the kernel (or<br>
> > elsewhere) I should be looking for the code which isn't meeting our<br>
> > Cog-nitive requirements?<br>
> > ><br>
> ><br>
> > I do not understand what problem or bug you are asking about. Is there<br>
> > some issue with Raspbian Linux that is causing a problem?<br>
> ><br>
> > Dave<br>
> ><br>
<br>
</div></blockquote></div><br><br clear="all"><div><br></div>-- <br>Casey Ransberger
</div>
<br></blockquote></div><br><br clear="all"><div><br></div>-- <br>best,<div>Eliot</div>
<br></blockquote></div><br><br clear="all"><div><br></div>-- <br>Casey Ransberger
</div>
</blockquote></div><br></div><br></blockquote></div><br><br clear="all"><div><br></div>-- <br>best,<div>Eliot</div>