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Thu, 31 Oct 2024 15:03:54 -0700 (PDT) Received: from [192.168.1.128] ([38.175.170.29]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4de049a45adsm465289173.148.2024.10.31.15.03.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 31 Oct 2024 15:03:53 -0700 (PDT) Message-ID: <2ff5424f-7fb0-4e67-a521-e309c870f229@linuxfoundation.org> Date: Thu, 31 Oct 2024 16:03:52 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] usb:core: Remove unused parameter struct usb_hcd *hcd in usb_hcd_unlink_urb_from_ep To: lizhe , gregkh@linuxfoundation.org, linus.walleij@linaro.org, stern@rowland.harvard.edu, ok@artecdesign.ee, mathias.nyman@intel.com, b-liu@ti.com, valentina.manea.m@gmail.com, shuah@kernel.org, i@zenithal.me, niko.mauno@vaisala.com, dvyukov@google.com, andreyknvl@gmail.com, tj@kernel.org, viro@zeniv.linux.org.uk, christophe.jaillet@wanadoo.fr, stanley_chang@realtek.com, sylv@sylv.io, lee@kernel.org, colin.i.king@gmail.com Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Shuah Khan References: <20241027163130.5368-1-sensor1010@163.com> <2692e3ef.b806.192d8f95cf3.Coremail.sensor1010@163.com> <663beaef-6e02-4a8c-b380-247050f8936e@linuxfoundation.org> <5e2b7e82.b980.192dd9ab0fc.Coremail.sensor1010@163.com> Content-Language: en-US From: Shuah Khan In-Reply-To: <5e2b7e82.b980.192dd9ab0fc.Coremail.sensor1010@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/30/24 07:25, lizhe wrote: > > Hi， Shuah Khan > > > *This sounds like this change isn't required? * > > **not, hcd in usb_hcd_unlink_urb_from_ep() is a redundant operation, although the cost of a single instance is minimal, the cumulative cost can be significant, > > such as when copying a large file to a USB drive. I am not convinced this change helps. I would rather keep the hcd argument to keep the api balanced and be able to debug a problem that requires the hcd to urb association. What are the performance numbers you are seeing with and without your patch when copying a large file to a USB drive? > > *Right. Can you quantify the overhead?* > > Quantifying it is merely to illustrate the benefits it brings > > because removing it has no drawbacks, the benefits of removing HCD are obvious, > There are drawbacks as pointed out in the above paragraph. The benefits of removing HCD are not obvious to me. Maybe you can provide them by answering the performance numbers with and without your patch when copying a large file to a USB drive keeping all other variables the same. thanks, -- Shuah