Bug 1179042 - Add a script for analyzing memory blocks using a heap s…

…can DMD log. r=njn DONTBUILD

Based on:
https://github.com/amccreight/heapgraph/blob/0a68e57a2c8cecb529dd5eab865bcd60dee6235e/dmd/block_analyzer.py

memory/replace/dmd/block_analyzer.py

@@ -0,0 +1,265 @@
+#!/usr/bin/python
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# From a scan mode DMD log, extract some information about a
+# particular block, such as its allocation stack or which other blocks
+# contain pointers to it. This can be useful when investigating leaks
+# caused by unknown references to refcounted objects.
+
+import json
+import gzip
+import sys
+import argparse
+import re
+
+
+# The DMD output version this script handles.
+outputVersion = 4
+
+# If --ignore-alloc-fns is specified, stack frames containing functions that
+# match these strings will be removed from the *start* of stack traces. (Once
+# we hit a non-matching frame, any subsequent frames won't be removed even if
+# they do match.)
+allocatorFns = [
+    'malloc (',
+    'replace_malloc',
+    'replace_calloc',
+    'replace_realloc',
+    'replace_memalign',
+    'replace_posix_memalign',
+    'malloc_zone_malloc',
+    'moz_xmalloc',
+    'moz_xcalloc',
+    'moz_xrealloc',
+    'operator new(',
+    'operator new[](',
+    'g_malloc',
+    'g_slice_alloc',
+    'callocCanGC',
+    'reallocCanGC',
+    'vpx_malloc',
+    'vpx_calloc',
+    'vpx_realloc',
+    'vpx_memalign',
+    'js_malloc',
+    'js_calloc',
+    'js_realloc',
+    'pod_malloc',
+    'pod_calloc',
+    'pod_realloc',
+    'nsTArrayInfallibleAllocator::Malloc',
+    # This one necessary to fully filter some sequences of allocation functions
+    # that happen in practice. Note that ??? entries that follow non-allocation
+    # functions won't be stripped, as explained above.
+    '???',
+]
+
+####
+
+# Command line arguments
+
+def range_1_24(string):
+    value = int(string)
+    if value < 1 or value > 24:
+        msg = '{:s} is not in the range 1..24'.format(string)
+        raise argparse.ArgumentTypeError(msg)
+    return value
+
+parser = argparse.ArgumentParser(description='Analyze the heap graph to find out things about an object. \
+By default this prints out information about blocks that point to the given block.')
+
+parser.add_argument('dmd_log_file_name',
+                    help='clamped DMD log file name')
+
+parser.add_argument('block',
+                    help='address of the block of interest')
+
+parser.add_argument('--info', dest='info', action='store_true',
+                    default=False,
+                    help='Print out information about the block.')
+
+parser.add_argument('-sfl', '--max-stack-frame-length', type=int,
+                    default=150,
+                    help='Maximum number of characters to print from each stack frame')
+
+parser.add_argument('-a', '--ignore-alloc-fns', action='store_true',
+                    help='ignore allocation functions at the start of traces')
+
+parser.add_argument('-f', '--max-frames', type=range_1_24,
+                    help='maximum number of frames to consider in each trace')
+
+parser.add_argument('-c', '--chain-reports', action='store_true',
+                    help='if only one block is found to hold onto the object, report the next one, too')
+
+
+####
+
+
+class BlockData:
+    def __init__(self, json_block):
+        self.addr = json_block['addr']
+
+        if 'contents' in json_block:
+            contents = json_block['contents']
+        else:
+            contents = []
+        self.contents = []
+        for c in contents:
+            self.contents.append(int(c, 16))
+
+        self.req_size = json_block['req']
+
+        self.alloc_stack = json_block['alloc']
+
+
+def print_trace_segment(args, stacks, block):
+    (traceTable, frameTable) = stacks
+
+    for l in traceTable[block.alloc_stack]:
+        # The 5: is to remove the bogus leading "#00: " from the stack frame.
+        print ' ', frameTable[l][5:args.max_stack_frame_length]
+
+
+def show_referrers(args, blocks, stacks, block):
+    visited = set([])
+
+    anyFound = False
+
+    while True:
+        referrers = {}
+
+        for b, data in blocks.iteritems():
+            which_edge = 0
+            for e in data.contents:
+                if e == block:
+                    # 8 is the number of bytes per word on a 64-bit system.
+                    # XXX This means that this output will be wrong for logs from 32-bit systems!
+                    referrers.setdefault(b, []).append(8 * which_edge)
+                    anyFound = True
+                which_edge += 1
+
+        for r in referrers:
+            sys.stdout.write('0x{} size = {} bytes'.format(blocks[r].addr, blocks[r].req_size))
+            plural = 's' if len(referrers[r]) > 1 else ''
+            sys.stdout.write(' at byte offset' + plural + ' ' + (', '.join(str(x) for x in referrers[r])))
+            print
+            print_trace_segment(args, stacks, blocks[r])
+            print
+
+        if args.chain_reports:
+            if len(referrers) == 0:
+                sys.stdout.write('Found no more referrers.\n')
+                break
+            if len(referrers) > 1:
+                sys.stdout.write('Found too many referrers.\n')
+                break
+
+            sys.stdout.write('Chaining to next referrer.\n\n')
+            for r in referrers:
+                block = r
+            if block in visited:
+                sys.stdout.write('Found a loop.\n')
+                break
+            visited.add(block)
+        else:
+            break
+
+    if not anyFound:
+        print 'No referrers found.'
+
+
+def show_block_info(args, blocks, stacks, block):
+    b = blocks[block]
+    sys.stdout.write('block: 0x{}\n'.format(b.addr))
+    sys.stdout.write('requested size: {} bytes\n'.format(b.req_size))
+    sys.stdout.write('\n')
+    sys.stdout.write('block contents: ')
+    for c in b.contents:
+        v = '0' if c == 0 else blocks[c].addr
+        sys.stdout.write('0x{} '.format(v))
+    sys.stdout.write('\n\n')
+    sys.stdout.write('allocation stack:\n')
+    print_trace_segment(args, stacks, b)
+    return
+
+
+def cleanupTraceTable(args, frameTable, traceTable):
+    # Remove allocation functions at the start of traces.
+    if args.ignore_alloc_fns:
+        # Build a regexp that matches every function in allocatorFns.
+        escapedAllocatorFns = map(re.escape, allocatorFns)
+        fn_re = re.compile('|'.join(escapedAllocatorFns))
+
+        # Remove allocator fns from each stack trace.
+        for traceKey, frameKeys in traceTable.items():
+            numSkippedFrames = 0
+            for frameKey in frameKeys:
+                frameDesc = frameTable[frameKey]
+                if re.search(fn_re, frameDesc):
+                    numSkippedFrames += 1
+                else:
+                    break
+            if numSkippedFrames > 0:
+                traceTable[traceKey] = frameKeys[numSkippedFrames:]
+
+    # Trim the number of frames.
+    for traceKey, frameKeys in traceTable.items():
+        if len(frameKeys) > args.max_frames:
+            traceTable[traceKey] = frameKeys[:args.max_frames]
+
+
+def loadGraph(options):
+    # Handle gzipped input if necessary.
+    isZipped = options.dmd_log_file_name.endswith('.gz')
+    opener = gzip.open if isZipped else open
+
+    with opener(options.dmd_log_file_name, 'rb') as f:
+        j = json.load(f)
+
+    if j['version'] != outputVersion:
+        raise Exception("'version' property isn't '{:d}'".format(outputVersion))
+
+    invocation = j['invocation']
+    sampleBelowSize = invocation['sampleBelowSize']
+    heapIsSampled = sampleBelowSize > 1
+    if heapIsSampled:
+        raise Exception("Heap analysis is not going to work with sampled blocks.")
+
+    block_list = j['blockList']
+    blocks = {}
+
+    for json_block in block_list:
+        blocks[int(json_block['addr'], 16)] = BlockData(json_block)
+
+    traceTable = j['traceTable']
+    frameTable = j['frameTable']
+
+    cleanupTraceTable(options, frameTable, traceTable)
+
+    return (blocks, (traceTable, frameTable))
+
+
+def analyzeLogs():
+    options = parser.parse_args()
+
+    (blocks, stacks) = loadGraph(options)
+
+    block = int(options.block, 16)
+
+    if not block in blocks:
+        print 'Object', block, 'not found in traces.'
+        print 'It could still be the target of some nodes.'
+        return
+
+    if options.info:
+        show_block_info(options, blocks, stacks, block)
+        return
+
+    show_referrers(options, blocks, stacks, block)
+
+
+if __name__ == "__main__":
+    analyzeLogs()