Re: [gentoo-dev] python-2.3.2 testing required - gentoo-dev

From:	Alastair Tse <liquidx@g.o>
To:	gentoo-dev@g.o
Subject:	Re: [gentoo-dev] python-2.3.2 testing required
Date:	Mon, 17 Nov 2003 00:29:46
Message-Id:	`1069028971.19556.39.camel@huggins.eng.cam.ac.uk`
In Reply to:	[gentoo-dev] python-2.3.2 testing required by Alastair Tse

1

On Wed, 2003-11-12 at 18:46, Alastair Tse wrote:

2

> The reason why I'm not making this default is because UCS4 python uses

3

> more memory. An example is supybot (Python IRC bot) that uses 8M for

4

> UCS2 and 13M for UCS4. But note that this example is not scientific

5

> because the machines were different in kernel version, compiler and

6

> compiler optimisations.

7

8

I've found a little spare time this weekend to do a little bit of memory

9

benchmarking to prove/disprove my point about UCS4 using more memory

10

than UCS2.

11

12

I wrote and conducted 2 simple tests that I thought were relevant to

13

Python on Gentoo. The two tests I conducted were:

14

15

1. Generating a large number of Python Unicode Strings and recording the

16

memory usage.

17

2. Running "emerge" on various different options and recording the

18

memory usage.

19

20

The results demonstrate that UCS4 is more memory hungry _only_ if a

21

script/module/application uses unicode strings. This means any bindings

22

that use PyUnicode_* objects (for example, pygtk) or any script that

23

uses unicode strings. If a script/module/application does not use

24

unicode objects, it suffers from no noticable memory impact.

25

26

The numbers reported are averages from 3 or more runs. In nearly all

27

cases, the memory usage was constant.

28

29

Results:

30

========

31

1 : Generating Unicode Multi-Byte Strings (1 to 10000) strings

32

(String Size of 256 mbchars stored in a regular python list)

33

-------------------------------------------------------------------

34

Strings: (UCS2) Mem   RSS  Shared (UCS4) Mem  RSS  Shared    %+

35

1               1839  710  1535          1839 711 1535       0

36

10              1871  712  1535          1871 717 1535       0

37

100             1904  765  1535          1971 830 1535       3.5

38

1000            2465  1336 1535          3102 1960 1535      25.84

39

10000           8213  7052 1535          14445 13309 1535    75.80

40

41

2 : Generating Unicode ASCII Strings (1 to 10000) strings

42

(String Size of 256 chars stored in a regular python list)

43

-------------------------------------------------------------------

44

Strings: (UCS2) Mem   RSS  Shared (UCS4) Mem  RSS  Shared    %+

45

1               1839  710  1535          1839 711  1535      0

46

10              1871  712  1535          1871 717  1535      0 

47

100             1904  765  1535          1971 830  1535      3.5

48

1000            2465  1336 1535          3102 1960 1535      25.84

49

10000           8213  7053 1535          14445 13309 1535    75.80

50

51

3: Max Memory Usage under "emerge -p kde"

52

-------------------------------------------------------------------

53

      Mem  RSS  Shared

54

UCS2: 3222 1893 1955

55

UCS4: 3123 1769 1955

56

57

4: Max Memory Usage under "emerge search kde"

58

-------------------------------------------------------------------

59

      Mem  RSS  Shared

60

UCS2: 3221 1898 1955

61

UCS4: 3160 1803 1955

62

63

Discussion

64

==========

65

66

There are two immediate observations. One is that UCS4 does use more

67

memory compared to UCS2 when unicode strings are involved. From Test 1

68

and 2, the VM has an overhead of 1.8M and as more strings are created,

69

their memory usage difference steadily increase to 75% difference.

70

71

The other observation is that if there are is no unicode usage in

72

application, like "emerge", there is virtually no impact. Actually, in

73

this case, you'll find that UCS4 uses about 60K ot 100K less memory than

74

UCS2. I don't have an explanation for that behaviour.

75

76

Other observations that can be made which do not relate to the UCS2/UCS4

77

benchmark is that it doesn't matter if you are primarily dealing with

78

ASCII or Multi-Byte (eg, CJK characters) strings. As soon as they are

79

cast as unicode objects, they use more memory. Note that the two runs

80

have identical memory usage, that is not a mistake.

81

82

Another one is that 'emerge' uses the same amount of memory regardless

83

of what is being run. I had an informal test running just "emerge info"

84

and it still used approximately the same memory as running more

85

complicated things like merging packages or searching the package

86

database.

87

88

Other Details

89

=============

90

The above results were run with dev-lang/python-2.3.2-r1 with:

91

Kernel 2.6.0-test9-mm1

92

Glibc-2.3.2-r8 (w/ nptl)

93

GCC-3.3.2

94

Portage 2.0.49-r16

95

96

The raw logs for the tests and the scripts used can be found at:

97

http://dev.gentoo.org/~liquidx/python-test/

98

99

Remarks

100

=======

101

102

After running these tests, I still divided about whether UCS4 should be

103

enabled by default. I'm not seeing the added benefits of UCS4 in

104

contrast with the memory usage increase it brings. Yet, it also seems

105

like the "right" thing to do for m17n support.

106

107

Cheers,

108

--

109

Alastair 'liquidx' Tse

110

 >> Gentoo Developer

111

 >> http://www.liquidx.net/ | http://dev.gentoo.org/~liquidx/

Gentoo Archives: gentoo-dev

Attachments

Replies

1	On Wed, 2003-11-12 at 18:46, Alastair Tse wrote:
2	> The reason why I'm not making this default is because UCS4 python uses
3	> more memory. An example is supybot (Python IRC bot) that uses 8M for
4	> UCS2 and 13M for UCS4. But note that this example is not scientific
5	> because the machines were different in kernel version, compiler and
6	> compiler optimisations.
7
8	I've found a little spare time this weekend to do a little bit of memory
9	benchmarking to prove/disprove my point about UCS4 using more memory
10	than UCS2.
11
12	I wrote and conducted 2 simple tests that I thought were relevant to
13	Python on Gentoo. The two tests I conducted were:
14
15	1. Generating a large number of Python Unicode Strings and recording the
16	memory usage.
17	2. Running "emerge" on various different options and recording the
18	memory usage.
19
20	The results demonstrate that UCS4 is more memory hungry _only_ if a
21	script/module/application uses unicode strings. This means any bindings
22	that use PyUnicode_* objects (for example, pygtk) or any script that
23	uses unicode strings. If a script/module/application does not use
24	unicode objects, it suffers from no noticable memory impact.
25
26	The numbers reported are averages from 3 or more runs. In nearly all
27	cases, the memory usage was constant.
28
29	Results:
30	========
31	1 : Generating Unicode Multi-Byte Strings (1 to 10000) strings
32	(String Size of 256 mbchars stored in a regular python list)
33	-------------------------------------------------------------------
34	Strings: (UCS2) Mem RSS Shared (UCS4) Mem RSS Shared %+
35	1 1839 710 1535 1839 711 1535 0
36	10 1871 712 1535 1871 717 1535 0
37	100 1904 765 1535 1971 830 1535 3.5
38	1000 2465 1336 1535 3102 1960 1535 25.84
39	10000 8213 7052 1535 14445 13309 1535 75.80
40
41	2 : Generating Unicode ASCII Strings (1 to 10000) strings
42	(String Size of 256 chars stored in a regular python list)
43	-------------------------------------------------------------------
44	Strings: (UCS2) Mem RSS Shared (UCS4) Mem RSS Shared %+
45	1 1839 710 1535 1839 711 1535 0
46	10 1871 712 1535 1871 717 1535 0
47	100 1904 765 1535 1971 830 1535 3.5
48	1000 2465 1336 1535 3102 1960 1535 25.84
49	10000 8213 7053 1535 14445 13309 1535 75.80
50
51	3: Max Memory Usage under "emerge -p kde"
52	-------------------------------------------------------------------
53	Mem RSS Shared
54	UCS2: 3222 1893 1955
55	UCS4: 3123 1769 1955
56
57	4: Max Memory Usage under "emerge search kde"
58	-------------------------------------------------------------------
59	Mem RSS Shared
60	UCS2: 3221 1898 1955
61	UCS4: 3160 1803 1955
62
63	Discussion
64	==========
65
66	There are two immediate observations. One is that UCS4 does use more
67	memory compared to UCS2 when unicode strings are involved. From Test 1
68	and 2, the VM has an overhead of 1.8M and as more strings are created,
69	their memory usage difference steadily increase to 75% difference.
70
71	The other observation is that if there are is no unicode usage in
72	application, like "emerge", there is virtually no impact. Actually, in
73	this case, you'll find that UCS4 uses about 60K ot 100K less memory than
74	UCS2. I don't have an explanation for that behaviour.
75
76	Other observations that can be made which do not relate to the UCS2/UCS4
77	benchmark is that it doesn't matter if you are primarily dealing with
78	ASCII or Multi-Byte (eg, CJK characters) strings. As soon as they are
79	cast as unicode objects, they use more memory. Note that the two runs
80	have identical memory usage, that is not a mistake.
81
82	Another one is that 'emerge' uses the same amount of memory regardless
83	of what is being run. I had an informal test running just "emerge info"
84	and it still used approximately the same memory as running more
85	complicated things like merging packages or searching the package
86	database.
87
88	Other Details
89	=============
90	The above results were run with dev-lang/python-2.3.2-r1 with:
91	Kernel 2.6.0-test9-mm1
92	Glibc-2.3.2-r8 (w/ nptl)
93	GCC-3.3.2
94	Portage 2.0.49-r16
95
96	The raw logs for the tests and the scripts used can be found at:
97	http://dev.gentoo.org/~liquidx/python-test/
98
99	Remarks
100	=======
101
102	After running these tests, I still divided about whether UCS4 should be
103	enabled by default. I'm not seeing the added benefits of UCS4 in
104	contrast with the memory usage increase it brings. Yet, it also seems
105	like the "right" thing to do for m17n support.
106
107	Cheers,
108	--
109	Alastair 'liquidx' Tse
110	>> Gentoo Developer
111	>> http://www.liquidx.net/ \| http://dev.gentoo.org/~liquidx/