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Sat, 08 Mar 2025 08:35:34 -0800 (PST) Received: from eleanor-wkdl ([140.116.96.203]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-224109ddbdcsm48671545ad.51.2025.03.08.08.35.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Mar 2025 08:35:33 -0800 (PST) Date: Sun, 9 Mar 2025 00:35:29 +0800 From: Yu-Chun Lin To: Simon Horman Cc: shshaikh@marvell.com, manishc@marvell.com, GR-Linux-NIC-Dev@marvell.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jserv@ccns.ncku.edu.tw, visitorckw@gmail.com Subject: Re: [PATCH net-next] qlcnic: Optimize performance by replacing rw_lock with spinlock Message-ID: References: <20250306163124.127473-1-eleanor15x@gmail.com> <20250307132929.GI3666230@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250307132929.GI3666230@kernel.org> On Fri, Mar 07, 2025 at 01:29:29PM +0000, Simon Horman wrote: > On Fri, Mar 07, 2025 at 12:31:24AM +0800, Yu-Chun Lin wrote: > > The 'crb_lock', an rwlock, is only used by writers, making it functionally > > equivalent to a spinlock. > > > > According to Documentation/locking/spinlocks.rst: > > > > "Reader-writer locks require more atomic memory operations than simple > > spinlocks. Unless the reader critical section is long, you are better > > off just using spinlocks." > > > > Since read_lock() is never called, switching to a spinlock reduces > > overhead and improves efficiency. > > > > Signed-off-by: Yu-Chun Lin > > Hi Yu-Chun Lin, > > Thanks for your patch. > > My main question is if you have hardware to test this? > And if so, was a benefit observed? > > If not, my feeling is that although your change looks > correct, we'd be better off taking the lower risk option > of leaving things be. Hi Simon I perform a compile test to ensure correctness. But I don't have the hardware to run a full test. Yu-Chun Lin