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From: Yuyang Du <yuyang.du@intel.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: peterz@infradead.org, mingo@kernel.org,
	linux-kernel@vger.kernel.org, bsegall@google.com, pjt@google.com,
	morten.rasmussen@arm.com, vincent.guittot@linaro.org,
	juri.lelli@arm.com
Subject: Re: [PATCH 1/4] sched/fair: Optimize sum computation with a lookup table
Date: Tue, 12 Apr 2016 03:17:12 +0800	[thread overview]
Message-ID: <20160411191712.GG8697@intel.com> (raw)
In-Reply-To: <570BD7DF.6070400@arm.com>

On Mon, Apr 11, 2016 at 05:59:11PM +0100, Dietmar Eggemann wrote:
> On 10/04/16 23:36, Yuyang Du wrote:
> > __compute_runnable_contrib() uses a loop to compute sum, whereas a
> > table loopup can do it faster in a constant time.
> > 
> > The following python script can be used to generate the constants:
> > 
> > print " #:     yN_inv   yN_sum"
> > print "-----------------------"
> > y = (0.5)**(1/32.0)
> > x = 2**32
> > xx = 1024
> > for i in range(0, 32):
> > 	if i == 0:
> > 		x = x-1
> > 		xx = xx*y
> > 	else:
> > 		x = x*y
> > 		xx = int(xx*y + 1024*y)
> > 	print "%2d: %#x %8d" % (i, int(x), int(xx))
> > 
> > print " #:  sum_N32"
> > print "------------"
> > xxx = xx
> > for i in range(0, 11):
> > 	if i == 0:
> > 		xxx = xx
> > 	else:
> > 		xxx = xxx/2 + xx
> > 	print "%2d: %8d" % (i, xxx)
> >
> 
> IMHO, it would be nice to add this to the existing tool from the patch
> header of commit 5b51f2f80b3b
> ("sched: Make __update_entity_runnable_avg() fast") simply because people
> already use this one to tweak their pelt tables. Maybe something like
 
I'd prefer not, and recommend switching from the C program for this
kind of job. :)

  reply	other threads:[~2016-04-12  2:59 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-10 22:36 [PATCH 0/4] Optimize sched avg computation and implement flat util hierarchy Yuyang Du
2016-04-10 22:36 ` [PATCH 1/4] sched/fair: Optimize sum computation with a lookup table Yuyang Du
2016-04-11  9:08   ` Vincent Guittot
2016-04-11 10:41   ` Juri Lelli
2016-04-11 19:12     ` Yuyang Du
2016-04-12 10:14       ` Juri Lelli
2016-04-12 18:07         ` Yuyang Du
2016-04-13  9:11           ` Juri Lelli
2016-04-11 16:59   ` Dietmar Eggemann
2016-04-11 19:17     ` Yuyang Du [this message]
2016-04-12 14:19       ` Peter Zijlstra
2016-04-12 18:12         ` Yuyang Du
2016-04-11 23:21     ` Joe Perches
2016-04-12 12:02       ` Juri Lelli
2016-04-11 23:07   ` Joe Perches
2016-04-10 22:36 ` [PATCH 2/4] sched/fair: Drop out incomplete current period when sched averages accrue Yuyang Du
2016-04-11  9:08   ` Vincent Guittot
2016-04-11 19:41     ` Yuyang Du
2016-04-12 11:56       ` Vincent Guittot
2016-04-12 21:09         ` Yuyang Du
2016-04-13 11:11           ` Vincent Guittot
2016-04-12 12:02   ` Dietmar Eggemann
2016-04-12 20:14     ` Yuyang Du
2016-04-13  4:04       ` Joe Perches
2016-04-13  8:40       ` Morten Rasmussen
2016-04-13 15:13   ` Dietmar Eggemann
2016-04-13 15:28     ` Vincent Guittot
2016-04-13 16:20       ` Vincent Guittot
2016-04-13 18:44       ` Yuyang Du
2016-04-14 12:52         ` Dietmar Eggemann
2016-04-14 20:05           ` Yuyang Du
2016-04-18 17:59             ` Yuyang Du
2016-04-10 22:36 ` [PATCH 3/4] sched/fair: Modify accumulated sums for load/util averages Yuyang Du
2016-04-11 17:14   ` Dietmar Eggemann
2016-04-10 22:36 ` [PATCH 4/4] sched/fair: Implement flat hierarchical structure for util_avg Yuyang Du
2016-04-11 12:29   ` Vincent Guittot
2016-04-11 20:37     ` Yuyang Du
2016-04-13 11:27       ` Vincent Guittot
2016-04-13 18:20         ` Yuyang Du

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