linux-kernel - Re: [RFC/RFT PATCH v3] sched: automated per tty task groups

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Date:	Thu, 11 Nov 2010 20:15:56 +0100
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Mike Galbraith <efault@....de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/RFT PATCH v3] sched: automated per tty task groups

On 2010.11.11 at 08:26 -0700, Mike Galbraith wrote:
> I _finally_ got back to this yesterday, and implemented your suggestion,
> though with a couple minor variations.  Putting the autogroup pointer in
> the signal struct didn't look right to me, so I plugged it into the task
> struct instead.  I also didn't refcount taskgroups, wanted the patchlet
> to be as self-contained as possible, so refcounted the autogroup struct
> instead.  I also left group movement on tty disassociation in place, but
> may nuke it.
...
> 
> With taskset -c 3 make -j 10 running..
> 
> taskset -c 3 ./wakeup-latency& sleep 30;killall wakeup-latency
> 
> without:
> maximum latency: 42963.2 µs
> average latency: 9077.0 µs
> missed timer events: 0
> 
> with:
> maximum latency: 4160.7 µs
> average latency: 149.4 µs
> missed timer events: 0

Just to add some data; here are the results from my machine (AMD 4
cores) running a -j4 kernel build, while I browsed the web:

1) perf sched record sleep 30

without:
total_wakeups: 44306
avg_wakeup_latency (ns): 36784
min_wakeup_latency (ns): 0
max_wakeup_latency (ns): 9378852

with:
total_wakeups: 43836
avg_wakeup_latency (ns): 67607
min_wakeup_latency (ns): 0
max_wakeup_latency (ns): 8983036

2) perf record -a -e sched:sched_switch -e sched:sched_wakeup sleep 10

without:
total_wakeups: 13195
avg_wakeup_latency (ns): 48484
min_wakeup_latency (ns): 0
max_wakeup_latency (ns): 8722497

with:
total_wakeups: 14106
avg_wakeup_latency (ns): 92532
min_wakeup_latency (ns): 20
max_wakeup_latency (ns): 5642393

So the avg_wakeup_latency nearly doubled with your patch, while the
max_wakeup_latency is lowered by a good amount.

-- 
Markus
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