From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB6C6183CA6 for ; Thu, 12 Jun 2025 12:23:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749730982; cv=none; b=MnyBKppzHLJTkvD1xvxW/UJoTeypLBUEjAPHqkIPDnk1ZBJKT6A+1DU4X+liRX8jyxvjc9RHkqxYNISFRoqJBzzi4/2DR0Do6UdI7HoBJeLMpJQo/h+vqj+ZzzsQ0WaCztFM3znTreRm81O9JGFWoI7aeOIdOw1wV7uKIdHAnWQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749730982; c=relaxed/simple; bh=R7fiw18KFaC+ydgxJ99RdUFN4AZj6Eiraj7ACYY5yZA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lIv0v8JI2DYQfZfC1VOommWWnfTbPIET5Q+S//VYz6fwqfrAGiEQkj/SKVV46k+uGMD0mKlkm7zxCkzgKbRj3gp5jHcsUBN0CirQnUjSCqP9Zp/n548QiaIEOwFllmq9B2KlBn5itNOtG3voI1oxPM0OmF9OyRXu8qwvGkOCjqo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=sRgDlUB2; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="sRgDlUB2" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=R9iXmNo70wFagHxjbWOlzebsUOjkG7VJgtdusCP+k38=; b=sRgDlUB2nTuSJCTLuvTdbpeefK CgSP/+eSxWrnM1yzv2yFmIRVE9NhhWykyoFUT3YVAb6nwHCtsiV3jJpw4t85Ha5yYYw4qvSpJ6ZWy QMnXfP95V5IWFwYsq/IkWc6jFkhxWyFp2gOtAwGXV10uAwZtXaZZ0CFJKhhDhkRjzn/iR6kv65Zj0 iCsoVSsY855gSnGz9wPolKbmRuwTN6wqVmzsmCPS0cNvpK+vHQq1i+lwfwr4MqETu0qp61BH6zPRk qm1RCCQ5nZRoqbF7RedDasX14+3+BhwLXBIUjmLgNWEyvuwQ+9NQ4YRcD8F6jIVgZsVG+AdwnNqBU 7tQLdY4A==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uPgxQ-0000000DF7X-1dX9; Thu, 12 Jun 2025 12:23:00 +0000 Date: Thu, 12 Jun 2025 05:23:00 -0700 From: Christoph Hellwig To: Jens Axboe Cc: Christoph Hellwig , "Mohamed Abuelfotoh, Hazem" , "linux-block@vger.kernel.org" Subject: Re: [PATCH] block: use plug request list tail for one-shot backmerge attempt Message-ID: References: <4856d1fc-543d-4622-9872-6ca66e8e7352@kernel.dk> <82020a7f-adbc-4b3e-8edd-99aba5172510@amazon.com> <045d300e-9b52-4ead-8664-2cea6354f5bf@kernel.dk> <505e4900-b814-47cd-9572-c0172fa0d01e@kernel.dk> Precedence: bulk X-Mailing-List: linux-block@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: <505e4900-b814-47cd-9572-c0172fa0d01e@kernel.dk> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Thu, Jun 12, 2025 at 06:21:14AM -0600, Jens Axboe wrote: > It's certainly going to make the cached handling more expensive, as the > doubly linked behavior there is just pointless. Generally LIFO behavior > there is preferable. I'd strongly suggest we use the doubly linked side > for dispatch, and retain singly linked for cached + completion. If not > I'm 100% sure we're going to be revisiting this again down the line, and > redo those parts yet again. Yeah. For cached requests and completions it might even make sense to have a simple fixed size array FIFO buffer..