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Thu, 12 Jun 2025 04:53:07 -0700 (PDT) Message-ID: Date: Thu, 12 Jun 2025 05:53:06 -0600 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH, RFC] block: always use a list_head for requests To: Christoph Hellwig Cc: abuehaze@amazon.com, linux-block@vger.kernel.org, ming.lei@redhat.com References: <20250612074245.2718371-1-hch@lst.de> Content-Language: en-US From: Jens Axboe In-Reply-To: <20250612074245.2718371-1-hch@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/12/25 1:42 AM, Christoph Hellwig wrote: > Turn the remaining lists of requests into the standard doubly linked > list. This removes a lot of hairy list manipulation code and allows > east reverse walking of the lists, which will be needed to improve > merging. > > XXX: the ublk queue_rqs code is pretty much broken here, because > it's so different from the other drivers and I don't understand it. First of all, we're definitely not doing this for 6.16-rc, and secondly it'd need to be properly tested in terms of performance implications as well. I'm somewhat annoyed that ordered plug lists turned into this, which I already strongly suspected would be the case back then. And doubly so that a really basic performance regression was also caused by that, and then the proposed "fix" is to go further into the "let's slow down the fast path" of code. Yes deleting some code is nice, but let's not pretend that it's free. -- Jens Axboe