I/O schedulers and performance -3-

I/O schedulers and their impact on performance 

(part 3)

for setup refer to part 2

What is being tested ?

• SQlite insert
• SQlite update
• SQlite delete

==> Using AndroBench v3.4 default settings

==> Each available scheduler is tested 3 times (same schedulers as previous post, i tried 10 times with fiops, but results are still inaccurate, so 3 times is enough not to waste time.)

Results : 
RAW data : the table displays mean result (out of 3) and related standard deviation to show how (in)consistent some results are.

in red : standard deviation that overrides the cut off (>2)

all results in TPS (Transaction per second)

IO scheduler	SQlite insert	SQlite update	SQlite delete	total
fiops	40,97	41,07	41,48	41,17
stdev	1,49	1,59	2,09	1,72
noop	42,21	40,13	42,08	41,47
stdev	0,91	2,60	1,76	1,76
bfq	41,35	35,26	36,94	37,85
stdev	1,70	2,32	1,98	2,00
cfq	40,82	40,70	40,87	40,79
stdev	2,96	1,54	1,03	1,84
deadline	40,84	38,75	41,86	40,48
stdev	2,62	0,86	3,60	2,36
zen	42,93	38,90	40,11	40,65
stdev	0,36	1,23	2,11	1,23
vr	41,79	38,67	41,00	40,49
stdev	0,67	1,74	1,07	1,16
row	39,09	41,32	40,75	40,39
stdev	5,07	2,65	3,18	3,63
sio	39,88	41,87	42,16	41,30
stdev	2,28	2,23	1,56	2,02

Following graphs display Sequential and Random Read/Write per Scheduler

As we can see, results are not much different from a scheduler to another

Though we can see that bfq is a bit behind

To better discriminate the good and the evil, i tried to take the median result as 100% (median is not modified by extreme values contrary to average/mean)

==> remember : this is a delta% against median (100%), that way a little difference looks big (mostly because of the chosen scale)

How to read the graph?

Same as previous post

What does that show?

• A lot, and it is not easy to extract things from it : 
• A scheduler that is good in SQlite insert is bat at update (and vice versa) : zen and sio mostly
• fiops is balanced but not extraordinary performant

Let's see the global graph 

• fiops seems to stay at the first place (mostly thanks to sequential read and write, it is not the best for SQlite)
• noop is the more balance and can be a good alternative
• bfq is clearly the worst here.

Since i'm not really sure how to conclude .... do it yourself ;)

==> These results are not god's speaking, and may be different with other tests/benchmarks AND devices.

What are the limits?

• Lack of accuracy with only 3 test per scheduler (and high results dispersion)
• These results are device dependent, kernel dependent, ROM dependent AND emmc type dependent (MotoG could be built with at least 4 different memory chips)
• Delta% against median is not the best to compare but was the easiest here (i could not put TPS, IOPS and MB/s in the same chart because of scaling)

Don't forget to read other I/O performances related posts : 

I/O schedulers and performance

I/O schedulers and performance -2-

Various conditions and I/O Performance

I/O schedulers and performance -2-

I/O schedulers and their impact on performance 

(part 2)

For details about I/O schedulers (what are they?) refer to the previous article

My current set up : 

• Motorola MotoG
• memory chipset : emmc: 8GB Sandisk REV=06 PRV=07 TYPE=17
• CM11-20140517-Nightly 
• RenderKernel r17
• 192-1190MHz
• gov : intellidemand

 Benchmark used : AndroBench v3.4

What is being tested ?

• Sequential Read (MB/s)
• Sequential Write (MB/s)
• Random Read (IOPS)
• Random Write (IOPS)

==> Using AndroBench v3.4 default settings

==> Each available scheduler is tested 3 times

• fiops
• noop
• bfq
• cfq
• deadline
• zen
• vr
• row
• sio

Results : 
RAW data : the table displays mean result (out of 3) and related standard deviation to show how (in)consistent some results are.

IO scheduler	seq read (MB/s)	seq write (MB/s)	rd read (IOPS)	rd write (IOPS)
fiops	62,76	15,61	1379,42	236,48
stdev	3,39	2,77	21,64	17,15
noop	59,34	13,43	1329,92	231,53
stdev	3,51	0,42	44,79	4,30
bfq	54,62	12,12	1320,23	231,39
stdev	1,53	0,49	25,45	2,11
cfq	55,31	14,37	1322,95	226,21
stdev	0,59	0,98	1,22	14,56
deadline	53,37	13,18	1335,51	229,98
stdev	5,51	1,14	26,91	6,46
zen	57,54	13,28	1383,16	232,40
stdev	1,18	1,93	39,88	14,18
vr	53,91	14,54	1352,52	226,86
stdev	1,22	1,15	22,62	1,95
row	57,88	13,66	1351,85	220,26
stdev	0,53	0,90	38,84	14,24
sio	58,32	13,26	1375,62	229,29
stdev	1,27	0,49	18,06	8,30

Following graphs display Sequential and Random Read/Write per Scheduler

The higher the better.

As we can see, results are not much different from a scheduler to another (unsignificant differences for Random IO)

Though we can see that fiops is a bit above the others (Zen, sio, noop and row are not that bad!)

To better discriminate the good and the evil, i tried to take the median result as 100% (median is not modified by extreme values contrary to average/mean)

==> remember : this is a delta% against median (100%), that way a little difference looks big (mostly because of the chosen scale)

How to read the graph?

With median value as 100%, 

• fiops is 109% in sequential read, 116% in sequential write, 102% in radom read and 103% in radom write
• bfq is 94% in sequential read, 90% in sequential write, 97% in radom read and 100% in radom write

What does that show?

• fiops seems to be the best here
• Zen, noop, sio and row are quite similar
• cfq and vr are behind in sequential read but better in sequential write
• deadline and bfq are worst here

==> These results are not god's speaking, and may be differents with other tests/benchmarks AND devices.

(i may test SQlite insert, update and delete later, perhaps these will change results?? )

What are the limits?

• Lack of accuracy with only 3 test per scheduler (and high results dispersion)
• These results are device dependent, kernel dependent, ROM dependent AND emmc type dependent (MotoG could be built with at least 4 different memory chips)
• Delta% against median is not the best to compare but was the easiest here (i could not put IOPS and MB/s in the same chart because of scaling)

Don't forget to read other I/O performances related posts : 

I/O schedulers and performance

I/O schedulers and performance -3-

Various conditions and I/O Performance