06468a15d5
Change-Id: I923ace7bedf022d49222e71c96c7e4c20f90e6cb Reviewed-on: https://gerrit.libreoffice.org/c/core/+/142521 Tested-by: Jenkins Reviewed-by: Hossein <hossein@libreoffice.org>
155 lines
6.8 KiB
Python
Executable file
155 lines
6.8 KiB
Python
Executable file
#!/usr/bin/python3
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#
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# Find holes in structures, so that we can pack them and improve our memory density.
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#
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# In order to make this work, you need to
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# (1) Be operating in a workspace where you have a __NON-DEBUG__ build of LibreOffice, but __WITH SYMBOLS__.
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# (A debug build has different sizes for some things in the standard library.)
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# (2) First run the unusedfields loplugin to generate a log file
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# (3) Install the pahole stuff into your gdb, I used this one:
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# https://github.com/PhilArmstrong/pahole-gdb
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# (4) Run the script
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# ./compilerplugins/clang/pahole-all-classes.py
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#
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import _thread
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import io
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import os
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import subprocess
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import re
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# search for all the class names in the file produced by the unusedfields loplugin
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#a = subprocess.Popen("grep 'definition:' workdir/loplugin.unusedfields.log | sort -u", stdout=subprocess.PIPE, shell=True)
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a = subprocess.Popen("cat n1", stdout=subprocess.PIPE, shell=True)
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classSet = set()
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classSourceLocDict = dict()
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locToClassDict = dict()
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with a.stdout as txt:
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for line in txt:
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tokens = line.decode('utf8').strip().split("\t")
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className = tokens[2].strip()
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srcLoc = tokens[5].strip()
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# ignore things like unions
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if "anonymous" in className: continue
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# ignore duplicates
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if className in classSet: continue
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classSet.add(className)
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classSourceLocDict[className] = srcLoc
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locToClassDict[srcLoc] = className
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a.terminate()
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# Some of the pahole commands are going to fail, and I cannot read the error stream and the input stream
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# together because python has no way of (easily) doing a non-blocking read.
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# So I have to write the commands out using a background thread, and then read the entire resulting
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# stream out below.
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def write_pahole_commands(classes):
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for className in classes:
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stdin.write("echo " + className + " " + classSourceLocDict[className] + "\n")
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stdin.write("pahole " + className + "\n")
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stdin.flush()
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stdin.write("echo all-done\n")
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stdin.flush()
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stdin.close() # only way to make it flush the last echo command
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# Use generator because lines often end up merged together in gdb's output, and we need
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# to split them up, and that creates a mess in the parsing logic.
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def read_generator(gdbOutput):
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while True:
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line = gdbOutput.readline();
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if line == "": return # end of file
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line = line.decode('utf8').strip()
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print("gdb: " + line)
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for split in line.split("(gdb)"):
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split = split.strip()
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if len(split) == 0: continue
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if "all-done" in split: return
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yield split
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# build list of classes sorted by source location to increase the chances of
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# processing stuff stored in the same DSO together
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sortedLocs = sorted(locToClassDict.keys())
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classList = list()
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for src in sortedLocs:
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if "/inc/" in src or "include/" in src:
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classList.append(locToClassDict[src])
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with open("compilerplugins/clang/pahole.results", "wt") as f:
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# Process 400 classes at a time, otherwise gdb's memory usage blows up and kills the machine
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# This number is chosen to make gdb peak at around 8G.
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while len(classList) > 0:
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currClassList = classList[0:500];
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classList = classList[500:]
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gdbProc = subprocess.Popen("gdb", stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True)
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stdin = io.TextIOWrapper(gdbProc.stdin, 'utf-8')
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# make gdb load all the debugging info
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stdin.write("set confirm off\n")
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# make gdb not wrap output and mess up my parsing
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stdin.write("set width unlimited\n")
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for filename in sorted(os.listdir('instdir/program')):
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if filename.endswith(".so"):
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stdin.write("add-symbol-file instdir/program/" + filename + "\n")
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stdin.flush()
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_thread.start_new_thread( write_pahole_commands, (currClassList,) )
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firstLineRegex = re.compile(r"/\*\s+(\d+)\s+\*/ struct") # /* 16 */ struct Foo
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fieldLineRegex = re.compile(r"/\*\s+(\d+)\s+(\d+)\s+\*/ ") # /* 12 8 */ class rtl::OUString aName
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holeLineRegex = re.compile(r"/\* XXX (\d+) bit hole, try to pack \*/")
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# sometimes pahole can't determine the size of a sub-struct, and then it returns bad data
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bogusLineRegex = re.compile(r"/\*\s+\d+\s+0\s+\*/")
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structLines = list()
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foundHole = False
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cumulativeHoleBits = 0
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alignedStructSize = 0
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foundBogusLine = False
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# pahole doesn't report space at the end of the structure, so work it out myself
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sizeOfStructWithoutPadding = 0
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for line in read_generator(gdbProc.stdout):
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structLines.append(line)
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firstLineMatch = firstLineRegex.match(line)
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if firstLineMatch:
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alignedStructSize = int(firstLineMatch.group(1))
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structLines.clear()
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structLines.append(line)
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holeLineMatch = holeLineRegex.match(line)
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if holeLineMatch:
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foundHole = True
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cumulativeHoleBits += int(holeLineMatch.group(1))
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fieldLineMatch = fieldLineRegex.match(line)
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if fieldLineMatch:
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fieldPosInBytes = int(fieldLineMatch.group(1))
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fieldSizeInBytes = int(fieldLineMatch.group(2))
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sizeOfStructWithoutPadding = fieldPosInBytes + fieldSizeInBytes
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if bogusLineRegex.match(line):
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foundBogusLine = True
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if line == "}":
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# Ignore very large structs, packing those is not going to help much, and
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# re-organising them can make them much less readable.
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if foundHole and len(structLines) < 16 and alignedStructSize < 100 and not foundBogusLine:
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# Verify that, after packing, and compiler alignment, the new structure will be actually smaller.
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# Sometimes, we can save space, but the compiler will align the structure such that we don't
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# actually save any space.
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# TODO improve detection of the required alignment for a structure
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holeAtEnd = alignedStructSize - sizeOfStructWithoutPadding
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potentialSpace = (cumulativeHoleBits / 8) + holeAtEnd
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if potentialSpace >= 8:
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for line in structLines:
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f.write(line + "\n")
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if holeAtEnd > 0:
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f.write("hole at end of struct: " + str(holeAtEnd) + "\n")
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f.write("\n")
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# reset state
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structLines.clear()
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foundHole = False
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cumulativeHoleBits = 0
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structSize = 0
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foundBogusLine = False
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actualStructSize = 0
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gdbProc.terminate()
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