1661689 - Add documentation on using bloaty to compare binary size of two revisions

Status: NEW

(Firefox Build System :: General, task)

Description

[Simon Giesecke [:sg] [he/him]]

I have a script to compare two revisions with bloaty producing a nice report:

#!/bin/sh -eORIGINALREV=$(hg id --num)BASEREV=$1

function binary-lto-build() {
    MOZCONFIG=mozconfig.trace-lto ./mach build && cp -H obj-x86_64-pc-linux-gnu-optimized-lto/dist/bin/libxul.so libxul.so-r$(hg id --num)
}

NEWREV=$2
if [ "$NEWREV" == "" ] ; then
  NEWREV=$(hg id --num)
else
  hg up $NEWREV
fi
if [ "$NEWREV" == "$BASEREV" ] ; then
    echo "New and base revisions are the same: $NEWREV"
    exit 1
fi
echo "Comparing new revision $NEWREV against base revision $BASEREV"
if [ ! -f libxul.so-r$NEWREV ] ; then binary-lto-build ; fi
if [ ! -f libxul.so-r$BASEREV ] ; then hg up $BASEREV ; binary-lto-build ; fi
hg up $ORIGINALREV

echo "Base revision:"
hg log -l1 -r$BASEREV
echo "Changes measured:"
hg log -r $BASEREV:$NEWREV-$BASEREV --stat
bloaty $BLOATYOPTS libxul.so-r$NEWREV -- libxul.so-r$BASEREV

using this mozconfig:

mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/obj-x86_64-pc-linux-gnu-optimized-lto
ac_add_options --disable-debug                                                 
ac_add_options --enable-optimize                                               
ac_add_options --enable-linker=lld
ac_add_options --enable-warnings-as-errors
ac_add_options --disable-hardening
ac_add_options --enable-lto=thin
AR=llvm-ar
RANLIB=llvm-ranlib
NM=llvm-nm

This could be added to the in-tree docs with some instructions for anyone interested.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee is inactive on Bugzilla, so the assignee is being reset.

Comment 2

[Marco Castelluccio [:marco]]

After adding documentation, we could also consider actually running this as part of CI and fail the job if there are large regressions.

Comment 3

[Mike Hommey [:glandium]]

We already have the overall libxul size tracked for regressions, I don't think tracking bloaty regressions would add much value.