netdev - Re: [PATCH 2/2] net: tcp: Add noinline_for_tracing annotation for tcp_drop

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Message-ID: <20241024210306.55559-1-kuniyu@amazon.com>
Date: Thu, 24 Oct 2024 14:03:06 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <dxu@...uu.xyz>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <kuniyu@...zon.com>, <laoar.shao@...il.com>,
	<menglong8.dong@...il.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH 2/2] net: tcp: Add noinline_for_tracing annotation for tcp_drop_reason()

From: "Daniel Xu" <dxu@...uu.xyz>
Date: Thu, 24 Oct 2024 13:52:06 -0700
> Hi Kuniyuki,
> 
> On Thu, Oct 24, 2024, at 12:13 PM, Kuniyuki Iwashima wrote:
> > From: Yafang Shao <laoar.shao@...il.com>
> > Date: Thu, 24 Oct 2024 17:37:42 +0800
> >> We previously hooked the tcp_drop_reason() function using BPF to monitor
> >> TCP drop reasons. However, after upgrading our compiler from GCC 9 to GCC
> >> 11, tcp_drop_reason() is now inlined, preventing us from hooking into it.
> >> To address this, it would be beneficial to make noinline explicitly for
> >> tracing.
> >> 
> >> Link: https://lore.kernel.org/netdev/CANn89iJuShCmidCi_ZkYABtmscwbVjhuDta1MS5LxV_4H9tKOA@mail.gmail.com/
> >> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> >> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> >> Cc: Menglong Dong <menglong8.dong@...il.com>
> >
> > I saw a somewhat related post yesterday.
> > https://x.com/__dxu/status/1849271647989068107
> 
> Glad to hear you're interested!
> 
> >
> > Daniel, could we apply your approach to this issue in the near future ?
> >
> 
> I suppose that depends on how you define "near". I'm being vague
> in that thread b/c we're still experimenting and have a couple things
> to look at still. But eventually, hopefully yes. Perhaps some time
> within a year if you had to press me.

Sorry, I didn't intend to rush you.  I was just curious if we would
need to revert the patch soon after being merged, so please take your
time :)

Thanks!