[Bug gold/20447] New: Slow linking with locale set to *.UTF-8

[pasko at chromium dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=20447

            Bug ID: 20447
           Summary: Slow linking with locale set to *.UTF-8
           Product: binutils
           Version: 2.24
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gold
          Assignee: ccoutant at gmail dot com
          Reporter: pasko at chromium dot org
                CC: ian at airs dot com
  Target Milestone: ---

shell> locale
LANG=en_US.UTF-8
LANGUAGE=en_US:
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

No short reproducer here, sorry. This was revealed during linking of Chrome for
Android (see instructions at [1]). We applied a workaround [2] when we noticed
that setting LC_ALL=C speeds things up by a factor of around 2.

The workaround was found by doing:
shell> perf record --pid=$PID_OF_LD_GOLD

Then 'perf report' said that >50% of perf samples had a call to
"__gconv_transform_utf8_internal", which looks like a performance bug.

References:
[1] build instructions for chrome_public_apk
    https://www.chromium.org/developers/how-tos/android-build-instructions

[2] Set LC_ALL=C for chrome link wrapper
    https://codereview.chromium.org/2190813002/

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