netdev - Re: [PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst

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Message-ID: <56aac06f-45b6-4a3c-9436-f400a4efd3d5@intel.com>
Date: Thu, 28 Aug 2025 17:33:36 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Yue Haibing <yuehaibing@...wei.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <horms@...nel.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] ipv6: sit: Add ipip6_tunnel_dst_find() for
 cleanup

From: Yue Haibing <yuehaibing@...wei.com>
Date: Thu, 28 Aug 2025 14:44:07 +0800

> On 2025/8/28 14:13, Yue Haibing wrote:
>> On 2025/8/27 22:45, Alexander Lobakin wrote:
>>> From: Yue Haibing <yuehaibing@...wei.com>
>>> Date: Wed, 27 Aug 2025 12:00:27 +0800
>>>
>>>> Extract the dst lookup logic from ipip6_tunnel_xmit() into new helper
>>>> ipip6_tunnel_dst_find() to reduce code duplication and enhance readability.
>>>>
>>>> No functional change intended.
>>>
>>> ...but bloat-o-meter stats would be nice to see here. I'm curious
>>> whether the object code got any changes or the compilers still just
>>> inline this function to both call sites.
> 
> On a x86_64, with allmodconfig:
> 
> ./scripts/bloat-o-meter -c net/ipv6/sit.o net/ipv6/sit-after.o
> add/remove: 2/0 grow/shrink: 1/1 up/down: 1770/-2152 (-382)
> Function                                     old     new   delta
> ipip6_tunnel_dst_find                          -    1697   +1697
> __pfx_ipip6_tunnel_dst_find                    -      64     +64
> ipip6_tunnel_xmit.isra.cold                   79      88      +9
> ipip6_tunnel_xmit.isra                      9910    7758   -2152

Oh okay, so it doesn't inline the function due to its size. Maybe it's
even better since we have a good object code reduction now and that
branch inside the func shouldn't hurt the performance much.

> Total: Before=70060, After=69678, chg -0.55%

Thanks,
Olek