ULatencyD Enters The Linux World

[TiborB]

Poelzi

I just want to thank you for your answers, I'm satisfied with them... thanks

[poelzi]

1) What if I start (by mistake or by chance) second instance of ulatencyd?

The worst thing that could happen ist that they move processes arround all the time, but that should not cause much trouble except more load.

2) what if there are two Xservers run on one box?

He should connect to all of them. I'm currently rewriting this module for better connection and lesser crude code ;-)

3) I must admit I'm not much familiar with cgroups and even what exactly your tool is doing. So I dont understand how your tool knows which application is "good" and which is "bad". For example, how it distinguishes opera from linuxdcpp or from some mp3 playing program... The active windows is not allways the right test, because mp3 player might not be in active window yet it needs some preference. Or do you have some list of applications split into some groups?

1. A program is only 'bad' when resources run into limitation. Currently only a memory protector exists and if he detects memory pressure, the largest programs are put into memory limitations.
I documented the default scheduler. As you can see, it does not say: this process is bad, but tries to find groups that belong together and gives each group an amount of cpu shares. As opposed the normal: each process gets the same amount of cpu share.
The rules in rules/media.lua schould set a flag on your mp3 program, so it gets more cpu share because it fits the requirements of the media group.

4) Do you trust ulatencyd that it would not do any serious harm? In other words, can I put it in the list of services started after boot of my box?

I'm running it all the time, but i will not suggest running it on a server currently. But for a desktop box it's fine.

5) Is it possible to measure effect of ulatencyd? Probably not I think...

Sure. If you run ulatencyd you can run tests/memleak for example without your box crashing. Or try something creazy like compiling the linux kernel with make -j 40 ;-)

I personally find by desktop much more smoother when it's running.

For your information - perhaps you can mentioned it somewhere - I found that for Arch Linux two PKGBUILDS were created in AUR (arch linux users will understand what it means) - ulatencyd and ulatencyd-git (http://aur.archlinux.org/packages.php)

Added it to the wiki, thanks.

[kbios]

I just installed a testing machine to write rules against the current container programs. But currently I can't say what will happen :-)

Thanks, that's very appreciated. Count on me for testing :-)

[poelzi]

Hi, I would like to try ULatencyD, but on the FAQ I read "You will not be able to run a different cgroups agent in parallel." Does this mean I will have problems with the linux-containers I'm using?
Thanks

I just installed a testing machine to write rules against the current container programs. But currently I can't say what will happen :-)

[poelzi]

ERROR: Unknown user-defined format specifier "cgroup".

Probably my ps is not new enough, ps -V returns:

procps version 3.2.8

This is neither your problem nor big problem, but some users can also run into this.... I just note that I have up-to-date arch linux

It seems that debian has patches for cgroups support that are not official.
Once i get time to write user programs i will add something that shows that :-)

[TiborB]

sorry for double post, it was confused because the first one did not show up immediately after I posted it..

I have small comment to your FAQ 1.1. Your command returns here

ERROR: Unknown user-defined format specifier "cgroup".

Probably my ps is not new enough, ps -V returns:

procps version 3.2.8

This is neither your problem nor big problem, but some users can also run into this.... I just note that I have up-to-date arch linux

[TiborB]

Hi Poelzi,

thanks for you prompt respond.

I installed today's version and indeed it is more verbose. Also, I started it from within Xserver and no crash this time.

I have another questions ...

1) What if I start (by mistake or by chance) second instance of ulatencyd?

2) what if there are two Xservers run on one box?

3) I must admit I'm not much familiar with cgroups and even what exactly your tool is doing. So I dont understand how your tool knows which application is "good" and which is "bad". For example, how it distinguishes opera from linuxdcpp or from some mp3 playing program... The active windows is not allways the right test, because mp3 player might not be in active window yet it needs some preference. Or do you have some list of applications split into some groups?

4) Do you trust ulatencyd that it would not do any serious harm? In other words, can I put it in the list of services started after boot of my box?

5) Is it possible to measure effect of ulatencyd? Probably not I think...

So these are my questions that accumulated in my head during the day

For your information - perhaps you can mentioned it somewhere - I found that for Arch Linux two PKGBUILDS were created in AUR (arch linux users will understand what it means) - ulatencyd and ulatencyd-git (http://aur.archlinux.org/packages.php)

That is all I have , thanks

Tibor

[TiborB]

Hi Poelzi,
thanks for you prompt respond.

I installed today's version and indeed it is more verbose. Also, I started it from within Xserver and no crash this time.

I have another questions ...

1) What if I start (by mistake or by chance) second instance of ulatencyd?

2) what if there are two Xservers run on one box?

3) I must admit I'm not much familiar with cgroups and even what exactly your tool is doing. So I dont understand how your tool knows which application is "good" and which is "bad". For example, how it distinguishes opera from linuxdcpp or from some mp3 playing program... The active windows is not allways the right test, because mp3 player might not be in active window yet it needs some preference. Or do you have some list of applications split into some groups?

4) Do you trust ulatencyd that it would not do any serious harm? In other words, can I put it in the list of services started after boot of my box?

5) Is it possible to measure effect of ulatencyd? Probably not I think...

So these are my questions that accumulated in my head during the day

For your information - perhaps you can mentioned it somewhere - I found that for Arch Linux two PKGBUILDS were created in AUR (arch linux users will understand what it means) - ulatencyd and ulatencyd-git (http://aur.archlinux.org/packages.php)

That is all I have , thanks

Tibor

[kbios]

That depends. If you are running it inside a container und the container system allows you to use cgroups, that should be fine.
If it is run on the host, you surely need a new scheduler configuration that takes into account that a process never ever gets moved outside the container it was created. I never looked into the namespace stuff, so i can honestly say: i don't know.
In general, it can work, at least it can be configured that way :-)

Thanks for your reply! I checked my setup and I found that all container processes are children of lxc-start. So would it be possible to write a rule (is it this what you mean with "new scheduler configuration"?) that prevents process that are child of lxc-start from being manipulated by ulatencyd? I searched the docs but I couldn't find anything like this. Thanks

[poelzi]

Hi, I would like to try ULatencyD, but on the FAQ I read "You will not be able to run a different cgroups agent in parallel." Does this mean I will have problems with the linux-containers I'm using?
Thanks

That depends. If you are running it inside a container und the container system allows you to use cgroups, that should be fine.
If it is run on the host, you surely need a new scheduler configuration that takes into account that a process never ever gets moved outside the container it was created. I never looked into the namespace stuff, so i can honestly say: i don't know.
In general, it can work, at least it can be configured that way :-)