Linux Performance Tuning - Page 4 - Overclock.net

enorbet2 · 01-11-09

Greetz
It is my understanding that the kernel is only one step removed from bios in terms of low level priority and like the bios it is read more or less constantly. The advent of on-demand modules a few years ago certainly and happily made kernel size a bit less important but AFAIK there still is considerable speed advantage to smaller kernels since module identification and loading is only part of what a kernel does. This is partly why after so many years and so much difficulty work is still being done on the HURD microkernel project.

An example that is easily tried and clocked for speed comparison is readily available with the latest versions of Slackware. Slack ships with multiple kernel images chosen according to perceived user hardware needs. The largest kernel appropriately labeled "huge" is around 5 MB in size. The "generic" kernel is around 2MB. My custom kernel is 1.3MB. It is quite easy to set up a system with all 3 kernels available with a menued bootloader. I assure you my custom kernel is noticeably faster than the generic kernel and majorly faster than the "huge" kernel. This remains true even if I customize the 2 default kernels to match for CPU type and other hardware sensitive issues. This is somewhat minimized by the fact that recent kernels are all compiled stock for i686 instead of i486 or even i386 common only a couple years ago for compatibility's sake.

Even raid and solid state drives still have read times slow enough to where the difference between a constantly read 1MB file and a 5MB file is cumulatively enormous in terms of system overhead. Reducing that overhead not only improves speed but enhances overall system timing since it is common for CPUs to spend considerable idle time waiting on ram let alone hard drive reads. Good examples of this issue can be found in how older systems of less than 2GHz CPUs with fast ram and hard drive systems are not altogether obsolete nor an agonizing experience subjectively to run. Another can be seen either in the gains that AMD enjoyed for awhile over Intel resulting in Intel finally caving in to the on-chip memory controller finally signaling the obsolescence of the Front Side Bus.

In short, there are still considerable gains to be made in custom kernels including smooth speed.
Jimmy

error10 · 01-11-09

I agree, building a custom kernel is one way to really speed up performance, but it's not something I would recommend to a beginning Linux user.

Buying an SSD drive, however, is.

Melcar · 01-12-09

Compiling a kernel is cheaper

.

enorbet2 · 01-12-09

Actually with one qualifier I disagree regarding newbies and custom kernels. IMHO as long a s a newbie understands how to add a 2nd kernel to the boot menu so the origibal is still available to fall back on when problems occur I see no problem.

Additionally there is a lot to be said for wiping that fear out from "jump street". I didn't really start learning about PCs until I learned I couldn't kill hardware from the keyboard. I had an old Tandy 8086 (with a soundcard no less!) running DOS v3 (with DOS in ROM too!) and after it was backed up I ran every executable I could find just to see what it did. I crashed but not burned many times and discovering how to recover both increased my abilities and my confidence.

I had held off having a computer because I couldn't see what I would want to compute that a sci calc couldn't do. Once I installed PCTools I reliazed a computer wasn't just a toolbox . it is ANY tool box. My first custom command line said "Yes_Master?" because I knew that baby's every nut and bolt both hard and soft and I'd learned it could be just about whatever I wanted it to be. However I was at first shocked when I saw DOS in ROM. Talk about cold molasses! But I digress..

Bottom line get your hands dirty as soon as possible once you've covered your butt. The worst you can do is lose data and time, but with backups that only leaves time and that is well spent learning you can be the driver instead of the passenger.

Jimmy

error10 · 01-12-09

Oh, I'd love to throw a noob right into kernel compilation, or even more interesting stuff, but it takes a certain kind of person. Most people just throw up their hands and say Linux sucks. (Of course it's because all they've ever known is Windows, and they think its many design flaws are the way things are supposed to be.)

enorbet2 · 01-12-09

Hey Error10 you know I think you've the exact point only from the backside in. What I mean is we who know Linux often make the mistake of trying to convince newbs of how much Linux can be like windows, run windows programs, etc instead of simply touting how Linux is different and better, of how while it doesn't necessarily require that you get down to nuts and bolts level you actually can in ways impossible for windows, partly due to it's proprietary nature but way more than that.

In the case of kernel compiles if you fail to get it right the first time (as most likely will) as long as you keep the shipped with kernel there is no loss other than a missed gain which can be fixed the next time. Even though the first look at all the config options is daunting it is also a peek at the power of what can be possible.

I think this sort of attitude opens the door for talking about how interdependent windows is with the "all eggs in one basket" approach where both the registry and the "Windows" and "Documents and Settings" directories require linking to everything essentially handicapping if not ruining the whole concept of a pre-emptive OpSys preventing crashes and data loss. On top of that there is just no easy equivalent way for windows to avoid reinstalling every last program on all reinstalls and some repair installs, which is so easily avoided with Linux. There are so many other points without even having to mention how unnecessary it makes piracy of programs but makes most drm issues irrelevant.

I know newbs contemplating trying Linux want to be reassured that Linux is like Windows but part of that is because they don't even know enough to ask better questions. They only know Windows so that's what they ask about. If instead of falling into that mode we offer up exciting differences or for that matter even limitations so we don't create more flamers by trying to bring someone in who may never "get it". I mean some people are just never (or not for a long time I think) going to go for Linux unless it is just like Windows and what's the value in that other than price ? After all there are actually some people who love cars but will never buy one with a stick transmission let alone pop the hood.

Bottom line why fight a battle we're unlikely to win when we can choose so many we can't possibly lose? Linux is *that* good but to stay that good it can't become Windows and should avoid most compromises to avoid becoming watered down and weak. I say give them the adventure!

error10 · 01-12-09

True enough. But some people just don't want an adventure. They want to get on eBay and buy $35 fans for $5. They want to chat with their friends and play their MP3s. They don't care about power. To them the computer is a toaster.

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Linux Performance Tuning

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