What are you doing now?

damgar · 05-16-2010, 11:11 AM

I'm waiting on breakfast and contractors.

brucehinrichs · 05-16-2010, 05:34 PM

Taking my latest install for a spin:

Code:

bruce@Frank2:~$ uname -a
Linux Frank2 2.6.33-4.dmz.1-liquorix-amd64 #1 ZEN SMP PREEMPT Wed May 12 23:07:52 CDT 2010 x86_64 GNU/Linux
bruce@Frank2:~$

Mol_Bolom · 05-16-2010, 07:28 PM

Started working on a script to compile the newer xorg (or scratch that idea and fuddle with the x11.SlackBuild), mesa, blah blah, as well as pondering if I should just go ahead and create an entire new directory under /usr (not a link) for xorg stuff.

Don't know why, but it has always bothered the living hell out of me having my console apps/docs/etc mixed in with my xorg apps/docs/etc...:/...

damgar · 05-16-2010, 07:31 PM

I'm making pork chops. Just got back from seeing Iron Man 2. Pretty good movie.

MrCode · 05-16-2010, 09:03 PM

I'm so bored, I just have to bring this up:

Why is it that the uname -a output for just about any recent kernel includes "PREEMPT"? I mean, isn't *every* Linux kernel pre-emptive multitasking now? Or the kernel of any modern PC operating system, for that matter.

...

exvor · 05-16-2010, 09:10 PM

No

you may find this article usefull http://kerneltrap.org/node/2702

MrCode · 05-16-2010, 09:13 PM

Oh...in that case I must be confusing it with the process pre-emption. Le whoops.

Er, wait...what's the difference between this "in-kernel" pre-emption and the "other" kind?

I'm a bit of a n00b to this OS/kernel stuff...

exvor · 05-16-2010, 09:43 PM

It had to do with how the kernel deals with process scheduling. You see contrary to popular belief and keeping withen the relm of single core cpu for simplicity, a computer processor can actually only run one thing at a time. It does this sorta put this on hold run a bit of this program put it on hold run another bit from this other program, and does it so quickly that it gives us the illusion of being able to run multiple programs at once.

I am no expert by anymeans... I couldent program myself out of a box, but there is a wealth of info on it online. This is part of the o'reilly series on such maters http://oreilly.com/catalog/linuxkern...pter/ch10.html

damgar · 05-16-2010, 09:55 PM

From make gconfig:

Quote:

No Forced Preemption (Server)

CONFIG_PREEMPT_NONE:

This is the traditional Linux preemption model, geared towards
throughput. It will still provide good latencies most of the
time, but there are no guarantees and occasional longer delays
are possible.

Select this option if you are building a kernel for a server or
scientific/computation system, or if you want to maximize the
raw processing power of the kernel, irrespective of scheduling
latencies.
----------------------------
Voluntary Kernel Preemption (Desktop)

CONFIG_PREEMPT_VOLUNTARY:

This option reduces the latency of the kernel by adding more
"explicit preemption points" to the kernel code. These new
preemption points have been selected to reduce the maximum
latency of rescheduling, providing faster application reactions,
at the cost of slightly lower throughput.

This allows reaction to interactive events by allowing a
low priority process to voluntarily preempt itself even if it
is in kernel mode executing a system call. This allows
applications to run more 'smoothly' even when the system is
under load.

Select this if you are building a kernel for a desktop system.
-----------------------------
Preemptible Kernel (Low-Latency Desktop)

CONFIG_PREEMPT:

This option reduces the latency of the kernel by making
all kernel code (that is not executing in a critical section)
preemptible. This allows reaction to interactive events by
permitting a low priority process to be preempted involuntarily
even if it is in kernel mode executing a system call and would
otherwise not be about to reach a natural preemption point.
This allows applications to run more 'smoothly' even when the
system is under load, at the cost of slightly lower throughput
and a slight runtime overhead to kernel code.

Select this if you are building a kernel for a desktop or
embedded system with latency requirements in the milliseconds
range.

exvor · 05-16-2010, 10:09 PM

Btw that book I linked is rather dated... year 2000 so I think some of this information like the kernel is no preemptive is incorrect now.

MrCode · 05-16-2010, 10:24 PM

Quote:

You see contrary to popular belief and keeping withen the relm of single core cpu for simplicity, a computer processor can actually only run one thing at a time. It does this sorta put this on hold run a bit of this program put it on hold run another bit from this other program, and does it so quickly that it gives us the illusion of being able to run multiple programs at once.

I was already aware of this, I was just a bit sketchy on the details. I found a decent site that does a fairly good job of explaining pre-emptive multitasking (and even goes a little bit into SMP). However, I take it as being a rather simplified explanation, and that the Linux kernel's scheduling methods are a bit more complex...?

Also, I think I should note that I've never written a single line of "bare metal" code in my life (unless you count Arduino sketches

), so what knowledge I do have is based on theory, rather than practice.

smeezekitty · 05-16-2010, 10:34 PM

Quote:

Originally Posted by MrCode

I was already aware of this, I was just a bit sketchy on the details. I found a decent site that does a fairly good job of explaining pre-emptive multitasking (and even goes a little bit into SMP). However, I take it as being a rather simplified explanation, and that the Linux kernel's scheduling methods are a bit more complex...?

Also, I think I should note that I've never written a single line of "bare metal" code in my life (unless you count Arduino sketches

), so what knowledge I do have is based on theory, rather than practice.

I cant take it any more - i need one now!!!!!!!

exvor · 05-16-2010, 10:54 PM

I am also rather curious as to what this arduino thingy is.

brucehinrichs · 05-16-2010, 10:59 PM

This is the board I have.

MrCode · 05-16-2010, 11:01 PM

Quote:

This is the board I have.

168 or 328? Mine's the 328. It's nice to have the extra little bit of memory