Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]
- From: Gene Heskett <gene.heskett@xxxxxxxxx>
- Date: Sun, 15 Apr 2007 12:58:48 -0400
On Sunday 15 April 2007, Con Kolivas wrote:
On Monday 16 April 2007 01:16, Gene Heskett wrote:
On Sunday 15 April 2007, Pekka Enberg wrote:
On 4/15/07, hui Bill Huey <billh@xxxxxxxxxxxxxxxxx> wrote:
The perception here is that there is that there is this expectation
that sections of the Linux kernel are intentionally "churn squated" to
prevent any other ideas from creeping in other than of the owner of
that subsytem
Strangely enough, my perception is that Ingo is simply trying to
address the issues Mike's testing discovered in RDSL and SD. It's not
surprising Ingo made it a separate patch set as Con has repeatedly
stated that the "problems" are in fact by design and won't be fixed.
I won't get into the middle of this just yet, not having decided which dog
I should bet on yet. I've been running 2.6.21-rc6 + Con's 0.40 patch for
about 24 hours, its been generally usable, but gzip still causes lots of 5
to 10+ second lags when its running. I'm coming to the conclusion that
gzip simply doesn't play well with others...
Actually Gene I think you're being bitten here by something I/O bound since
the cpu usage never tops out. If that's the case and gzip is dumping
truckloads of writes then you're suffering something that irks me even more
than the scheduler in linux, and that's how much writes hurt just about
everything else. Try your testcase with bzip2 instead (since that won't be
i/o bound), or drop your dirty ratio to as low as possible which helps a
little bit (5% is the minimum)
echo 5 > /proc/sys/vm/dirty_ratio
and finally try the braindead noop i/o scheduler as well.
echo noop > /sys/block/sda/queue/scheduler
(replace sda with your drive obviously).
I'd wager a big one that's what causes your gzip pain. If it wasn't for the
fact that I've decided to all but give up ever trying to provide code for
mainline again, trying my best to make writes hurt less on linux would be my
next big thing [tm].
Chuckle, possibly but then I'm not anything even remotely close to an expert
here Con, just reporting what I get. And I just rebooted to 2.6.21-rc6 +
sched-mike-5.patch for grins and giggles, or frowns and profanity as the case
may call for.
Oh and for the others watching, (points to vm hackers) I found a bug when
playing with the dirty ratio code. If you modify it to allow it drop below
5% but still above the minimum in the vm code, stalls happen somewhere in
the vm where nothing much happens for sometimes 20 or 30 seconds worst case
scenario. I had to drop a patch in 2.6.19 that allowed the dirty ratio to
be set ultra low because these stalls were gross.
I think I'd need a bit of tutoring on how to do that. I recall that one other
time, several weeks back, I thought I would try one of those famous echo this
/proc/that ideas that went by on this list, but even though I was root,apparently /proc was read-only AFAIWC.
Amazing to me, the cpu its using stays generally below 80%, and often
below 60%, even while the kmail composer has a full sentence in its buffer
that it still hasn't shown me when I switch to the htop screen to check,
and back to the kmail screen to see if its updated yet. The screen switch
doesn't seem to lag so I don't think renicing x would be helpfull. Those
are the obvious lags, and I'll build & reboot to the CFS patch at some
point this morning (whats left of it that is :). And report in due time
of course
And now I wonder if I applied the right patch. This one feels good ATM, but I
don't think its the CFS thingy. No, I'm sure of it now, none of the patches
I've saved say a thing about CFS. Backtrack up the list time I guess, ignore
me for the nonce.
--
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)
Microsoft: Re-inventing square wheels
-- From a Slashdot.org post
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