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Date:   Fri, 13 Sep 2019 07:42:15 +0200
From:   Ingo Molnar <mingo@kernel.org>
To:     Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        ndesaulniers@google.com,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Nadav Amit <namit@vmware.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH v3 6/6] x86: bug.h: use asm_inline in _BUG_FLAGS
 definitions
Message-ID: <20190913054215.GB118828@gmail.com>
References: <20190830231527.22304-1-linux@rasmusvillemoes.dk>
 <20190912221927.18641-1-linux@rasmusvillemoes.dk>
 <20190912221927.18641-7-linux@rasmusvillemoes.dk>
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* Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> This helps preventing a BUG* or WARN* in some static inline from
> preventing that (or one of its callers) being inlined, so should allow
> gcc to make better informed inlining decisions.
> 
> For example, with gcc 9.2, tcp_fastopen_no_cookie() vanishes from
> net/ipv4/tcp_fastopen.o. It does not itself have any BUG or WARN, but
> it calls dst_metric() which has a WARN_ON_ONCE - and despite that
> WARN_ON_ONCE vanishing since the condition is compile-time false,
> dst_metric() is apparently sufficiently "large" that when it gets
> inlined into tcp_fastopen_no_cookie(), the latter becomes too large
> for inlining.
> 
> Overall, if one asks size(1), .text decreases a little and .data
> increases by about the same amount (x86-64 defconfig)
> 
> $ size vmlinux.{before,after}
>    text    data     bss     dec     hex filename
> 19709726        5202600 1630280 26542606        195020e vmlinux.before
> 19709330        5203068 1630280 26542678        1950256 vmlinux.after
> 
> while bloat-o-meter says
> 
> add/remove: 10/28 grow/shrink: 103/51 up/down: 3669/-2854 (815)
> ...
> Total: Before=14783683, After=14784498, chg +0.01%
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo