Re: [PATCH 0/2] perf: we can now read separate debug-info files based on a build ID

[Dima Kogan <dima@secretsauce.net>]

Hi. This is a gentle ping. This patch fixes a real bug, and it'd be
great if it was merged.

Here's a demo. This is on a recent Debian/sid box, tracing malloc()
calls in emacs. The debug symbols for libc and emacs are split into
separate (installed) packages, as is the norm.

    $ perf probe -x /lib/x86_64-linux-gnu/libc-2.19.so --add malloc                                                          

    $ perf record -g -eprobe_libc:malloc -p `pidof emacs`

Before patch:

    $ perf script | head -n 10
    emacs  7750 [001] 353845.297868: probe_libc:malloc: (7f4fbde59020)
                       7c020 malloc (/lib/x86_64-linux-gnu/libc-2.19.so)
                      144877 [unknown] (/usr/bin/emacs-snapshot-lucid)
                      144989 [unknown] (/usr/bin/emacs-snapshot-lucid)
                      144bcc [unknown] (/usr/bin/emacs-snapshot-lucid)
                      15a91b [unknown] (/usr/bin/emacs-snapshot-lucid)
                       99f25 [unknown] (/usr/bin/emacs-snapshot-lucid)
                      199211 [unknown] (/usr/bin/emacs-snapshot-lucid)
                      1a0c6b [unknown] (/usr/bin/emacs-snapshot-lucid)
                       1ed86 [unknown] (/usr/bin/emacs-snapshot-lucid)

After patch:

    $ perf script | head -n 10 
    emacs  7750 [001] 353845.297868: probe_libc:malloc: (7f4fbde59020)
                       7c020 malloc (/lib/x86_64-linux-gnu/libc-2.19.so)
                      144877 allocate_string_data (/usr/bin/emacs-snapshot-lucid)
                      144989 make_uninit_multibyte_string (/usr/bin/emacs-snapshot-lucid)
                      144bcc make_uninit_string.part.18 (/usr/bin/emacs-snapshot-lucid)
                      15a91b make_buffer_string_both (/usr/bin/emacs-snapshot-lucid)
                       99f25 decode_coding_object (/usr/bin/emacs-snapshot-lucid)
                      199211 read_process_output (/usr/bin/emacs-snapshot-lucid)
                      1a0c6b wait_reading_process_output (/usr/bin/emacs-snapshot-lucid)
                       1ed86 sit_for (/usr/bin/emacs-snapshot-lucid)