Re: [PATCH dwarves 0/2] dwarf_loader: improve cus__merging_cu()

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Yonghong Song <yhs@fb.com>
Cc: "Arnaldo Carvalho de Melo" <arnaldo.melo@gmail.com>,
	dwarves@vger.kernel.org, "Alexei Starovoitov" <ast@kernel.org>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Bill Wendling" <morbo@google.com>,
	bpf@vger.kernel.org, "David Blaikie" <dblaikie@gmail.com>,
	"Fāng-ruì Sòng" <maskray@google.com>,
	kernel-team@fb.com, "Nick Desaulniers" <ndesaulniers@google.com>
Subject: Re: [PATCH dwarves 0/2] dwarf_loader: improve cus__merging_cu()
Date: Thu, 1 Apr 2021 09:59:19 -0300	[thread overview]
Message-ID: <YGXDp/AwQapX/wDj@kernel.org> (raw)
In-Reply-To: <20210401025815.2254256-1-yhs@fb.com>

Em Wed, Mar 31, 2021 at 07:58:15PM -0700, Yonghong Song escreveu:
> Function cus__merging_cu() is introduced in Commit 39227909db3c
> ("dwarf_loader: Permit merging all DWARF CU's for clang LTO built
> binary") to test whether cross-cu references may happen.
> The original implementation anticipates compilation flags
> in dwarf, but later some concerns about binary size surfaced
> and the decision is to scan .debug_abbrev as a faster way
> to check cross-cu references. Also putting a note in vmlinux
> to indicate whether lto is enabled for built or not can
> provide a much faster way.

Great work! Reviewing/testing right now.

- Arnaldo

> This patch set implemented this two approaches, first
> checking the note (in Patch #2), if not found, then
> check .debug_abbrev (in Patch #1).
> 
> Yonghong Song (2):
>   dwarf_loader: check .debug_abbrev for cross-cu references
>   dwarf_loader: check .notes section for lto build info
> 
>  dwarf_loader.c | 76 ++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 55 insertions(+), 21 deletions(-)
> 
> -- 
> 2.30.2
> 

-- 

- Arnaldo