Nat!'s Web Journal

I would have thought that Linux and RAIDing is something so common now, one wouldn't even need to think about it. But when I looked around for a new motherboard with an on board RAID controller and researched a little which controllers are supported best under Linux I found out, that there are only two controllers Highpoint and Promise, which one might consider. Nevertheless both of them apparently still need specific kernel versions or specific distributions and also have some other flaws

So I went with a software RAID and bought two identical Samsung 160 GB discs, whose serial numbers differ by 1. Installed them in the server and proceeded to put a partition on each of them before raiding them together with mkraid. Creating one big partition on each of the discs lead to slightly different sized partitions, so I had to manually size them to make then even. That I already found peculiar.

Then i raided them together for mirroring and came up with a RAID of about 800 MB. Surprise!

Both harddiscs had differing geometries!

bash-2.05# hdparm -g /dev/hdd

/dev/hdd:
 geometry     = 16709/255/63, sectors = 268435455, start = 0
bash-2.05# hdparm -g /dev/hdc

/dev/hdc:
 geometry     = 266305/16/63, sectors = 268435455, start = 0

A theory why there are different geometries in the two harddiscs is, that due to bad sectors there is an algorithm used by the harddisc vendor, that tries to compute a geometry, that is closest to the actual number of sectors available.

Now we will be mirroring with rsync.

Boring...

Doom 3 will contain satanistic sympols witch our precious youth will see! Some claims that they look more forward to doom 3 than the second coming of Jesus Christ. The madness and violence must stop NOW! Don't let ID Software ever release doom 3 or it won't be long before we'll have a youth full of devil woreshippers and another columbine highschool situation

I mean if you write a petition to the U.S. Congress, even with only three whole sentences, at least run a spell checker over it once. Everything else will be just unintentionally funny.

Also this gives me a public feedback and discussion venue for my sporadically appearing articles.

Weblog users have first crack at it. Tell me if anything is not working.

I also need the new article to have something to show for the grand opening of the Forum :)

C# appears to be winning, and that's a fundamentally better language. Though I in general still don't see the advantage of virtual machines on the application level for anything, except for browsers really.

operateAnnihilate uses plain [object method] calls. Fast operateAnnihilateFast is the one using function pointers. operateAnnihilateFastest is the new stuff :) The results were:

Starting operateAnnhilate...
Stopped operateAnnhilate 8891ms elapsed_
Starting operateAnnihilateFast...
Stopped operateAnnihilateFast 9717ms elapsed_
Starting operateAnnihilateFastest...
Stopped operateAnnihilateFastest 6456ms elapsed_

So I went over it with otool. To my pleasant surprise I noticed that with XCode 1.5 and the newest gcc installed, the dummy methods are indeed compiled to blr and blr only. Most optimal :). The function pointer call sequence itself, though is still quite lacking as one stall could easily be avoided.

At first I thought that maybe Apple took the suggestion and used function pointers itself, somehow more optimally... They don't.
Then I figured they might have implemented some of the Tiger techniques already... They haven't.
Then I traced through both codes with the debugger. Still the function pointer technique is about six instructions shorter...

Smells like a cache problem...

I have to admit that the PMC registers in the PPC 970 are just slightly :) beyond my comprehension. They seem to differ much from the 7450, where I have the documentation. Unfortunately the documentation for the PPC 970 monitoring registers are supposed to be described in detail in Book IV of the architecture guide, of which three volumes have been published...

If anyone has some more info about the PMC registers, please leave a comment or mail me.

Also I'd like to get the mysterious "cache problem" sorted out before.

I then got the idea that, since the 970 is derived from the POWER4, that maybe the performance monitoring unit of the 970 is a copy of that chip. Either I looked in all the wrong places, or the POWER4 / RS64 III CPU is much worse documented than the 970. Although it's the much older chip.

As - this being my holidays - I have a little time on my hand, I tried the amber, simg5, scrollpv combination from CHUD to see if that got me any futher. Unfortunately the last two tools are written in Java :) And scrollpv does not seem to be working correctly any more. What I could see, I didn't find more valuable, that what I could see in Shark.

So I am none the wiser.

I think looking through the architecture books, I can figure most of the events out by myself. This sorta reminds me of my earlier endeavors, which goes to show, that I haven't gotten anywhere :)

Die Termine für diese Saison sind soweit eingetragen, wie sie schon feststehen.

I am still procrastinating on the article, because I hope some fairy will reveal the PPC 970 cache secrets to me yet.

Starting operateAnnhilateNaive...
Stopped operateAnnhilateNaive 5289ms elapsed
Starting operateAnnhilate...
Stopped operateAnnhilate 3719ms elapsed
Starting operateAnnihilateFast...
Stopped operateAnnihilateFast 3494ms elapsed
Starting operateAnnihilateFastest...
Stopped operateAnnihilateFastest 2766ms elapsed

Oh oh wait, now the problem is back. Hurra.

Starting operateAnnhilateNaive...
Stopped operateAnnhilateNaive 5189ms elapsed
Starting operateAnnhilate...
Stopped operateAnnhilate 3641ms elapsed
Starting operateAnnihilateFast...
Stopped operateAnnihilateFast 4198ms elapsed
Starting operateAnnihilateFastest...
Stopped operateAnnihilateFastest 2617ms elapsed

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Configuration

If you like you can download the project. It's not polished, even has some cosmetic bugs, it doesn't have a unique icon. No homepage for it and no documentation. Realistically, I wont spend any more time on this.

It might be that you need MenuMeters installed to run this, because MenuMeters comes with a MenuCrack thingy, which could be neccessary.