1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
#!/usr/bin/python3
#
# Find holes in structures, so that we can pack them and improve our memory density.
#
# In order to make this work, you need to
# (1) Be operating in a workspace where you have a __NON-DEBUG__ build of LibreOffice, but __WITH SYMBOLS__.
# (A debug build has different sizes for some things in the standard library.)
# (2) First run the unusedfields loplugin to generate a log file
# (3) Install the pahole stuff into your gdb, I used this one:
# https://github.com/PhilArmstrong/pahole-gdb
# (4) Run the script
# ./compilerplugins/clang/pahole-all-classes.py
#
import _thread
import io
import os
import subprocess
import time
import re
# search for all the class names in the file produced by the unusedfields loplugin
#a = subprocess.Popen("grep 'definition:' workdir/loplugin.unusedfields.log | sort -u", stdout=subprocess.PIPE, shell=True)
a = subprocess.Popen("cat n1", stdout=subprocess.PIPE, shell=True)
classSet = set()
classSourceLocDict = dict()
locToClassDict = dict()
with a.stdout as txt:
for line in txt:
tokens = line.decode('utf8').strip().split("\t")
className = tokens[2].strip()
srcLoc = tokens[5].strip()
# ignore things like unions
if "anonymous" in className: continue
# ignore duplicates
if className in classSet: continue
classSet.add(className)
classSourceLocDict[className] = srcLoc
locToClassDict[srcLoc] = className
a.terminate()
# Some of the pahole commands are going to fail, and I cannot read the error stream and the input stream
# together because python has no way of (easily) doing a non-blocking read.
# So I have to write the commands out using a background thread, and then read the entire resulting
# stream out below.
def write_pahole_commands(classes):
for className in classes:
stdin.write("echo " + className + " " + classSourceLocDict[className] + "\n")
stdin.write("pahole " + className + "\n")
stdin.flush()
stdin.write("echo all-done\n")
stdin.flush()
stdin.close() # only way to make it flush the last echo command
# Use generator because lines often end up merged together in gdb's output, and we need
# to split them up, and that creates a mess in the parsing logic.
def read_generator(gdbOutput):
while True:
line = gdbOutput.readline();
if line == "": return # end of file
line = line.decode('utf8').strip()
print("gdb: " + line)
for split in line.split("(gdb)"):
split = split.strip()
if len(split) == 0: continue
if "all-done" in split: return
yield split
# build list of classes sorted by source location to increase the chances of
# processing stuff stored in the same DSO together
sortedLocs = sorted(locToClassDict.keys())
classList = list()
for src in sortedLocs:
if "include/" in src:
classList.append(locToClassDict[src])
with open("compilerplugins/clang/pahole.results", "wt") as f:
# Process 400 classes at a time, otherwise gdb's memory usage blows up and kills the machine
# This number is chosen to make gdb peak at around 8G.
while len(classList) > 0:
currClassList = classList[0:500];
classList = classList[500:]
gdbProc = subprocess.Popen("gdb", stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True)
stdin = io.TextIOWrapper(gdbProc.stdin, 'utf-8')
# make gdb load all the debugging info
stdin.write("set confirm off\n")
# make gdb not wrap output and mess up my parsing
stdin.write("set width unlimited\n")
for filename in sorted(os.listdir('instdir/program')):
if filename.endswith(".so"):
stdin.write("add-symbol-file instdir/program/" + filename + "\n")
stdin.flush()
_thread.start_new_thread( write_pahole_commands, (currClassList,) )
firstLineRegex = re.compile("/\*\s+(\d+)\s+\*/ struct") # /* 16 */ struct Foo
fieldLineRegex = re.compile("/\*\s+(\d+)\s+(\d+)\s+\*/ ") # /* 12 8 */ class rtl::OUString aName
holeLineRegex = re.compile("/\* XXX (\d+) bit hole, try to pack \*/")
# sometimes pahole can't determine the size of a sub-struct, and then it returns bad data
bogusLineRegex = re.compile("/\*\s+\d+\s+0\s+\*/")
structLines = list()
foundHole = False
cumulativeHoleBits = 0
alignedStructSize = 0
foundBogusLine = False
# pahole doesn't report space at the end of the structure, so work it out myself
sizeOfStructWithoutPadding = 0
for line in read_generator(gdbProc.stdout):
structLines.append(line)
firstLineMatch = firstLineRegex.match(line)
if firstLineMatch:
alignedStructSize = int(firstLineMatch.group(1))
structLines.clear()
structLines.append(line)
holeLineMatch = holeLineRegex.match(line)
if holeLineMatch:
foundHole = True
cumulativeHoleBits += int(holeLineMatch.group(1))
fieldLineMatch = fieldLineRegex.match(line)
if fieldLineMatch:
fieldPosInBytes = int(fieldLineMatch.group(1))
fieldSizeInBytes = int(fieldLineMatch.group(2))
sizeOfStructWithoutPadding = fieldPosInBytes + fieldSizeInBytes
if bogusLineRegex.match(line):
foundBogusLine = True
if line == "}":
# Ignore very large structs, packing those is not going to help much, and
# re-organising them can make them much less readable.
if foundHole and len(structLines) < 16 and alignedStructSize < 100 and not foundBogusLine:
# Verify that, after packing, and compiler alignment, the new structure will be actually smaller.
# Sometimes, we can save space, but the compiler will align the structure such that we don't
# actually save any space.
# TODO improve detection of the required alignment for a structure
holeAtEnd = alignedStructSize - sizeOfStructWithoutPadding
potentialSpace = (cumulativeHoleBits / 8) + holeAtEnd
if potentialSpace >= 8:
for line in structLines:
f.write(line + "\n")
if holeAtEnd > 0:
f.write("hole at end of struct: " + str(holeAtEnd) + "\n")
f.write("\n")
# reset state
structLines.clear()
foundHole = False
cumulativeHoleBits = 0
structSize = 0
foundBogusLine = False
actualStructSize = 0
gdbProc.terminate()
|
