linux-kernel - Re: [PATCH v2 12/28] kbuild: lto: limit inlining

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Message-ID: <202009031520.DCF0B90B65@keescook>
Date:   Thu, 3 Sep 2020 15:20:14 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v2 12/28] kbuild: lto: limit inlining

On Thu, Sep 03, 2020 at 01:30:37PM -0700, Sami Tolvanen wrote:
> This change limits function inlining across translation unit boundaries
> in order to reduce the binary size with LTO. The -import-instr-limit
> flag defines a size limit, as the number of LLVM IR instructions, for
> importing functions from other TUs, defaulting to 100.
> 
> Based on testing with arm64 defconfig, we found that a limit of 5 is a
> reasonable compromise between performance and binary size, reducing the
> size of a stripped vmlinux by 11%.
> 
> Suggested-by: George Burgess IV <gbiv@...gle.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook