Received-SPF: pass (google.com: domain of linux-kernel+bounces-201567-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Date: Wed, 5 Jun 2024 01:44:37 +0200
From: Andrew Lunn <andrew@lunn.ch>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Paolo Abeni <pabeni@redhat.com>,
	Mina Almasry <almasrymina@google.com>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Donald Hunter <donald.hunter@gmail.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Richard Henderson <richard.henderson@linaro.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Matt Turner <mattst88@gmail.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	Helge Deller <deller@gmx.de>, Andreas Larsson <andreas@gaisler.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Arnd Bergmann <arnd@arndb.de>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
	Yonghong Song <yonghong.song@linux.dev>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>,
	Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	David Ahern <dsahern@kernel.org>,
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
	Shuah Khan <shuah@kernel.org>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
	Pavel Begunkov <asml.silence@gmail.com>, David Wei <dw@davidwei.uk>,
	Yunsheng Lin <linyunsheng@huawei.com>,
	Shailend Chand <shailend@google.com>,
	Harshitha Ramamurthy <hramamurthy@google.com>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Jeroen de Borst <jeroendb@google.com>,
	Praveen Kaligineedi <pkaligineedi@google.com>,
	Willem de Bruijn <willemb@google.com>,
	Kaiyuan Zhang <kaiyuanz@google.com>
Subject: Re: [PATCH net-next v10 05/14] netdev: netdevice devmem allocator
Message-ID: <3be107ce-3d9f-4528-b9f7-1c9e38da0688@lunn.ch>
References: <20240530201616.1316526-1-almasrymina@google.com>
 <20240530201616.1316526-6-almasrymina@google.com>
 <bea8b8bf1630309bb004f614e4a3c7f684a6acb6.camel@redhat.com>
 <20240604121551.07192993@gandalf.local.home>
 <20240604163158.GB21513@ziepe.ca>
 <20240604124243.66203a46@gandalf.local.home>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240604124243.66203a46@gandalf.local.home>

> 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