Re: Renice X for cpu schedulers

Gene Heskett
2007-04-20T02:01:27Z

On Thursday 19 April 2007, Con Kolivas wrote:
>On Friday 20 April 2007 04:16, Gene Heskett wrote:
>> On Thursday 19 April 2007, Con Kolivas wrote:
>>
>> [and I snipped a good overview]
>>
>> >So yes go ahead and think up great ideas for other ways of metering out
>> > cpu bandwidth for different purposes, but for X, given the absurd
>> > simplicity of renicing, why keep fighting it? Again I reiterate that
>> > most users of SD have not found the need to renice X anyway except if
>> > they stick to old habits of make -j4 on uniprocessor and the like, and I
>> > expect that those on CFS and Nicksched would also have similar
>> > experiences.
>>
>> FWIW folks, I have never touched x's niceness, its running at the default
>> -1 for all of my so-called 'tests', and I have another set to be rebooted
>> to right now. And yes, my kernel makeit script uses -j4 by default, and
>> has used -j8 just for effects, which weren't all that different from what
>> I expected in 'abusing' a UP system that way. The system DID remain
>> usable, not snappy, but usable.
>
>Gene, you're agreeing with me. You've shown that you're very happy with a
> fair distribution of cpu and leaving X at nice 0.

I was quite happy till Ingo's first patch came out, and it was even better,
but I over-wrote it, and we're still figuring out just exactly what the magic
twanger was that made it all click for me. OTOH, I don't think that patch
passed muster with Mike G., either. We have obviously different workloads,
and critical points in them.

>> Having tried re-nicing X a while back, and having the rest of the system
>> suffer in quite obvious ways for even 1 + or - from its default felt
>> pretty bad from this users perspective.
>>
>> It is my considered opinion (yeah I know, I'm just a leaf in the hurricane
>> of this list) that if X has to be re-niced from the 1 point advantage its
>> had for ages, then something is basicly wrong with the overall scheduling,
>> cpu or i/o, or both in combination. FWIW I'm using cfq for i/o.
>
>It's those who want X to have an unfair advantage that want it to do
>something "special". Your agreement that it works fine at nice 0 shows you
>don't want it to have an unfair advantage. Others who want it to have an
>unfair advantage _can_ renice it if they desire. But if the cpu scheduler
>gives X an unfair advantage within the kernel by default then you have _no_
>choice. If you leave the choice up to userspace (renice or not) then both
>parties get their way. If you put it into the kernel only one party wins and
>there is no way for the Genes (and Cons) of this world to get it back.
>
>Your opinion is as valuable as eveyone else's Gene. It is hard to get people
>to speak on as frightening a playground as the linux kernel mailing list so
>please do.

In the FWIW category, htop has always told me that x is running at -1, not
zero. Now, I have NDI where this is actually set at, so I'd have to ask
stupid questions here if I did wanna play with it. Which I really don't, the
last time I tried to -5 x, kde got a whole lot LESS responsive. But heck,
2.6.2 was freshly minted then too and I've long since forgot how I went about
that unless I used htop to change it, the most likely scenario that I can
picture at this late date.

As for speaking my mind, yes, and I've been slapped down a few times, as much
because I do a lot of bitching and microscopic amounts of patch submission.
The only patch I ever submitted was for something in the floppy driver, way
back in the middle of 2.2 days, rejected because I didn't know how to use the
tools correctly. I didn't, so it was a shrug and my feelings weren't hurt.

Some see that as an unbalanced set of books and I'm aware of it. OTOH, I
think I do a pretty good job of playing the canary here, and that should be
worth something if for no other reason than I can turn into a burr under
somebodies saddle when things go all aglay. But I figure if its happening to
me, then if I don't fuss, and that gotcha gets into a distro kernel, there
are gonna be a hell of a lot more folks than me trying to grab the
microphone.

BTW, I'm glad you are feeling well enough to get into this again.

--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
There cannot be a crisis next week. My schedule is already full.
-- Henry Kissinger