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Diffstat (limited to 'memory/replace/dmd/block_analyzer.py')
| -rw-r--r-- | memory/replace/dmd/block_analyzer.py | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/memory/replace/dmd/block_analyzer.py b/memory/replace/dmd/block_analyzer.py new file mode 100644 index 0000000000..1f907b38a7 --- /dev/null +++ b/memory/replace/dmd/block_analyzer.py @@ -0,0 +1,292 @@ +#!/usr/bin/env python3 + +# 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 argparse +import gzip +import json +import re +import sys + +# The DMD output version this script handles. +outputVersion = 5 + +# 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", + "Allocator<ReplaceMallocBase>::malloc(", + "mozilla::dmd::StackTrace::Get(", + "mozilla::dmd::AllocCallback(", + "mozilla::dom::DOMArena::Allocate(", + # 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=300, + 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, + default=8, + 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.items(): + 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 "" + print( + " at byte offset" + + plural + + " " + + (", ".join(str(x) for x in referrers[r])) + ) + 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)) + + 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 block not in blocks: + print("Object " + options.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() |