BRBUILDLOG:command:br_prepare_repo binutils_gdb master ---> git remote prune origin ---> git pull --all Fetching origin Already up-to-date. Current top commit: commit 4838e44c8fcb2ce2316294a6f30b8d40343c36af Author: Simon Marchi Date: Tue Jun 25 14:22:30 2019 -0400 arm-tdep: sort mapping symbols after parsing all minimal symbols Somebody on IRC reported a while ago that loading a big ARM program in GDB was very slow. Their profiling pointed out that a big amount of time was spent in VEC_safe_insert (arm_mapping_symbol_s, *map_p, idx, &new_map_sym); I was able to verify this as well. ARM mapping symbols are special ELF symbols named $a, $d and $t indicating that symbols starting at this address up to the next mapping symbol (in terms of address) are of type "ARM code", "data" and "Thumb code", respectively. GDB records these symbols in vectors (one for each section) in arm-tdep.c. These vectors are sorted by symbol address, to allow for quick lookup. The current approach is to insert new symbols at the right position to keep the vectors sorted at all time. This is done based on the assumption that mapping symbols come already almost sorted from the binary, as explains this comment in arm_record_special_symbol: /* Assume that most mapping symbols appear in order of increasing value. If they were randomly distributed, it would be faster to always push here and then sort at first use. */ Well, it turns out this is not the case. The original reporter mentioned that mapping symbols in their binaries are not nearly sorted, and this is not my experience either (at least in the binary used in the benchmark below). So if the values don't come nearly sorted, doing insertions to keep the vectors sorted ends up being of the order of number_of_mapping_symbols ^ 2. This patch changes it just like the comment above says, to just append to the vector in arm_record_special_symbol and sort the vector on first use. Benchmark ========= I have done some benchmarks using an --enable-targets=all GDB, compiled with -O2, running on x86-64 and parsing file dce18d22e5c2ecb6a3a57372f4e6ef614130bc.debug from this package: https://launchpad.net/ubuntu/+source/firefox/66.0.3+build1-0ubuntu1/+build/16608691/+files/firefox-dbg_66.0.3+build1-0ubuntu1_armhf.deb This file is the separate debug info for libxul.so (part of firefox) for ARM. I have added some traces to measure the execution time of just elf_symtab_read and ran GDB like this: ./gdb --data-directory=data-directory -nx -batch .../path/to/usr/lib/debug/.build-id/65/dce18d22e5c2ecb6a3a57372f4e6ef614130bc.debug Since the new code sorts the vectors on first use, it would be difficult to benchmark it as-is and be fair, since the "before" version does more work in elf_symtab_read. So I have actually benchmarked a version of the patch that did sort all the vectors at the end of elf_symtab_read, so the sorting would be considered in the measured execution time. Here's the measured execution time of elf_symtab_read, averaged on 3 runs: insert sorted (before): 28.678s sort after (after): 1.760s And here's the total execution time of the command above (just one run). The time is now mostly spent in reading DWARF. insert sorted: 71.12s user 2.71s system 99% cpu 1:14.03 total sort after: 46.42s user 2.60s system 99% cpu 49.147 total I tried for fun on my Raspberry Pi 3, the run time of elf_symtab_read goes from ~259s to ~9s, reading the same file. gdb/ChangeLog: * arm-tdep.c (struct arm_per_objfile) : New field. (arm_find_mapping_symbol): Sort mapping symbol vectors on first use. (arm_record_special_symbol): Don't insert new symbol in sorted position, push it at the end. Outstanding patch: BRBUILDLOG:starttime:1561494755 BRBUILDLOG:stoptime:1561494758 BRBUILDLOG:duration:3 BRBUILDLOG:status:0