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Linux Kernel Hacker Interview @ Arstechnica
Posted by: Jim on: 01/22/2004 02:37 PM [ Print | 14 comment(s) ]
Three of the guys over at Arstechnica got together and interviewed Robert Love, a prominent Linux Kernel hacker. The topic of conversation? Version 2.6 of the Linux Kernel, of course.
Ars: What's going on with explicit hyperthreading2 support for Pentium 4? As we understand it, the 2.6 scheduler treats logical processor pairs as independent entities with independent caches and independent functional units. There's a batch scheduler in the works that promises to schedule things with an awareness that resources are shared, as well as scheduling similar-priority threads together. What's planned, ultimately, for this work?
Love: Optimizing for HT
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« 3dchips.net tests 10 Opteron coolers! · Linux Kernel Hacker Interview @ Arstechnica
· SCO attempts to involve Congress in perpetual Linux drama »
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dualboot_2xcpu Removed from forum Posts: 2396 Joined: 2001-07-16 |
![]() So is the way the linux kernel handles the SMP/SMT hardware efficient? /*asskoala if you reply to this please dont be biased against linux, I really want to know your opinion without all the bias on this matter.*/ alex I finally have SMP. Looking for the next Mrs. Right now (c) 2004. HEMI. |
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jives BP6 User Posts: 2399 Joined: 2001-05-18 |
![]() Hm makes since the problem making each logical CPU look as if it is a real CPU to the system. At least the Linux community is open about this and willing to see it as a problem that needs work. Any one know how Other OSs handle HT in MultiCPU systems? |
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i_wolf labhair dom as gaelige Posts: 2034 Joined: 2002-11-19 |
![]() i would love to see some HT benchmarks on and off with this new kernel. That was a good question about the efficiency of the 2.6 solution? I reckon benchmarks (real world) woudl be the only way to tell... Hung like a donkey. Go like a horse! |
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Jim_ Administrator Posts: 3574 Joined: 2000-03-15 |
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I'm open to other Linux benchmark suggestions as well. [url="http://www.2cpu.com"][size=1]2CPU.com[/url] - Because two are always better than one! [url="http://www.jimkirk.org"]jimkirk.org[/url] - Not a Myth any Longer. Just a Dad.[/size] |
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AssKoala Anti-Zealot @ GATech Posts: 3302 Joined: 2002-01-02 |
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I've done enough Kernel Hacking (and reading of documentation) to say no. Compared to the XP/2k3 Kernel Implementation, it looks like an undergrad project. I'm still working on learning all the Windows internals. The 2.6 Scheduler is a lot better than the crap they had in 2.4, though, so I give them credit. Actually, a friend of mine had to take the 2.6 Scheduler and implement it in the 2.4 Kernel as a weekend project in his CS class. I have to take that one next semester... Me Webpage | If you always think like an expert, you'll always be a beginner. | "A handful of knowledgeable people is more effective than an army of fools" -Writing Secure Code, 2nd Ed. |
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jives BP6 User Posts: 2399 Joined: 2001-05-18 |
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I'll take anything you want to do with compression, file compression (bzip2, gzip, etc), picture compression and/or video compression. The vast majority of tasks that I do that consume any noticeable amount of time normally involves compressing or decompressing data in some form. |
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jives BP6 User Posts: 2399 Joined: 2001-05-18 |
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So does Windows know the difference between the logical vs the physical and correct for that in the scheduler?
It |
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AssKoala Anti-Zealot @ GATech Posts: 3302 Joined: 2002-01-02 |
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Of course. XP and Server2003 do. That's one of the major differences between Windows 2000 and Windows XP. Me Webpage | If you always think like an expert, you'll always be a beginner. | "A handful of knowledgeable people is more effective than an army of fools" -Writing Secure Code, 2nd Ed. |
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i_wolf labhair dom as gaelige Posts: 2034 Joined: 2002-11-19 |
![]() Hi there Jim, Good call on the bench's. I can't wait to see what you got in store. bench's i would like to see.... audio compression: LAME mp3 encoding, Ogg encoding Vid encoding: xvid encoding Linpack compilation .... test how long it takes to compile kde (full) [joke.. this takes ages!!] 3d modelling. .... blender3d Could i ask you to try something actually while you are benchmarking. I presume you will be using the latest GCC to compile the source for the apps you will be using.... while you are doing that (i know its huge extra effort) but would you use Intel C Compiler as well (i think its free for linux for educational purposes... and it doesn't get any more educational than this!)... just to see how good properly optimized threaded code runs with the new kernel. Hung like a donkey. Go like a horse! |
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Jim_ Administrator Posts: 3574 Joined: 2000-03-15 |
![]() I'll look into it. I can't make any promises as this is a relatively large undertaking, but Hooz and I have been curious about Intel's compiler for quite some time. I'll probably run the numbers initially with GCC and then maybe, if I have time, I'll try out the Intel compiler as well. [url="http://www.2cpu.com"][size=1]2CPU.com[/url] - Because two are always better than one! [url="http://www.jimkirk.org"]jimkirk.org[/url] - Not a Myth any Longer. Just a Dad.[/size] |
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AssKoala Anti-Zealot @ GATech Posts: 3302 Joined: 2002-01-02 |
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If Intel's Linux-version Compiler has all the features of the Windows version, it'll produce some insanely fast code. I'd heard that its still missing some features, though. In Compiler benchmarks (benchmarking the code it compiles, not how long it takes), it blows past GCC, which lags behind MS Visual Studio. Especially with SSE2 compiles (I think in SSE2 Optimized code, it was at least triple Visual Studio and GCC's performance). Of course, GCC is about compiling on anything, not being the fastest. Me Webpage | If you always think like an expert, you'll always be a beginner. | "A handful of knowledgeable people is more effective than an army of fools" -Writing Secure Code, 2nd Ed. |
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i_wolf labhair dom as gaelige Posts: 2034 Joined: 2002-11-19 |
![]() the only problem is that it breaks compatibility with a LOT of gcc code. particularly it had probs with pre linking code for me on certain apps. But having said that that was on version 7 and im told version 8 is out now and has supposedly resolved this issue?! who knows. Funnily enough, code ive compiled myself in the past has seen more of an improvement on my opteron than xeon rig! who would have thunk it?! There was a discussion in ars before about version 7 ICC and that its heavy use of autovectorised SSE2 even in instances where it shouldn't be used... e.g. where IEEE floating point precision is required has meant that the resulting binary produces erronous results. I don't know enough to comment on that. Just read it yonks ago and it sounded like it should be taken with a grain of salt at the time. but still caught my interest. I think it was koepi or was it nick ... that compiled part of xvid code and said they got a free 10 to 20 percent improvement! (my own memory is a bit dodge) but this is a real impressive improvement. Jim/Hooz it would be awesome if you pull off these benchs! Hung like a donkey. Go like a horse! |
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Forge labhair dom as gaelige Posts: 720 Joined: 2001-05-12 |
![]() Maybe a little GCC vs. ICC on Opteron, too, if I can swing it. Could get nifty rates of change to graph, then, too, plus GCC32 and GCC64 code versus ICC32 code. No promises, though. I think I'm going to have a full plate for a while. Registered Linux user 82133 (li.org has a short memory) |
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jrv-austin Registered User Posts: 256 Joined: 2004-01-19 |
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Historically the goal on gcc was to generate "correct" code, which means it does what the source code intends (which may or may not be what the programmer intended!). An important bias in gcc is the need for maintainability. There are a lot of different processors supported, and a change for one processor must not make other processors less reliable. icc's emphasis on the other hand has always been speed of the generated code, and Intel has always been willing to run a lot of risks. I was the gcc x86 maintainer for a few years around 1990 and rejected numerous patches from Intel precisely because of the reliability issue. They'd send a patch, I'd run a test suite and get half a dozen bombs, and that was that. Generally they weren't interested in fixing it the issue and so the change was dropped - it was like they were paid to write code and not to debug it. The other problem is that the x86 violates the design criteria in gcc for the "weakest" processor supported. There are nowhere near enough registers for the reg allocator, and some instructions must use memory in unusual ways (float to int conversions). gcc's architecture was unfortunately set in the 1980s when nobody dreamed an x86 architecture would survive. icc and the Microsoft compilers have had the luxury of only 3-4 processors to consider, and weren't being done on volunteer time. Tyan K8W S2885, 2x Opteron 248, 8GB ECC DDR400, 3ware 8506-8 mirrored 2x Raptor 74, 2x 7k250 HP zx6000 1x 1.5 GHz 6MB Itanic2 |