linux-kernel - Re: [PATCH net-next v10 05/14] netdev: netdevice devmem allocator

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Message-ID: <3be107ce-3d9f-4528-b9f7-1c9e38da0688@lunn.ch>
Date: Wed, 5 Jun 2024 01:44:37 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Jason Gunthorpe <jgg@...pe.ca>, Paolo Abeni <pabeni@...hat.com>,
	Mina Almasry <almasrymina@...gle.com>, netdev@...r.kernel.org,
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Subject: Re: [PATCH net-next v10 05/14] netdev: netdevice devmem allocator

> Interesting, as I sped up the ftrace ring buffer by a substantial amount by
> adding strategic __always_inline, noinline, likely() and unlikely()
> throughout the code. It had to do with what was considered the fast path
> and slow path, and not actually the size of the function. gcc got it
> horribly wrong.

And what did the compiler people say when you reported gcc was getting
it wrong?

Our assumption is, the compiler is better than a human at deciding
this. Or at least, a human who does not spend a long time profiling
and tuning. If this assumption is not true, we probably should be
trying to figure out why, and improving the compiler when
possible. That will benefit everybody.

       Andrew