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 C4EFBF507 for ; Tue, 27 Aug 2024 04:38:16 +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=1724733498; cv=none; b=hFvJlM+ASzViBAfI+swciOoEtFjIypRArKupc2ja+ea/nOkHUJO5GshNB14ROo8WIfCfhqG10KfSCxKrNujo6y4dhbY/MGIu4Yfvt5dCT6itBvExjs7ngD+YXaUBhnhJDqEWdY3Nj8CTg3KCL1UcbqpdIxubroAVNXCqjvjrZP4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724733498; c=relaxed/simple; bh=XZqhGdAJwoHxiaDDZnYcXwmgEwbAQmGLn3u/oN2mPNA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YNTNBg0yfdYsddtTIx68l2MUx0k5BCAkzAfdhPpPAOf2WPqjxl0RFPga441cxLSXa6mz0E+le68t+cUPrWjZDSaVlhAeDynkYlyJyysxbgU67SQe1MIq5W8l+PnvdQDvTUT44qLwfYzamzqGQt4lR4XCpydO8WanP2UxugJkElw= 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=Mparv4E1; 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="Mparv4E1" 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=uKamNo9yoDuusn8fYAmJjQEz9iA3jZsbIcV03GuAiH4=; b=Mparv4E1GbsojXTrfRcJufzegh N16VKf04b/O7A7OcM6womR3ZmnPypdDJhSA9NLro1JlQvFO8D4vOBBXf7UkzauPuKHUjIWvQZCVKe M5OiqNQbV78v303VJ1njBCbw84e0OFJh6z2WWPRVlTkAXaUnoKR2x+fjW4qdICFPQpw7pTCLu36dp SPB/rfFP8RocToJV1sC29BgFnh+hoWOlL4ff4DD1eOZeITLnYavN3gUEbwB8cd8h1PPXKESO6Fh+b 9qOaHgS4K9Zc6hflBh9Wot1RsgYS6306bJ409yPZMhqL5zrXa70CvFvZwbwdNn0ufP6NoD1dRpcg8 LgulPUsg==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sinyC-00000009iqj-0wEh; Tue, 27 Aug 2024 04:38:16 +0000 Date: Mon, 26 Aug 2024 21:38:16 -0700 From: Christoph Hellwig To: Dave Chinner Cc: "Darrick J. Wong" , hch@lst.de, linux-xfs@vger.kernel.org Subject: Re: [PATCH 11/24] xfs: create incore realtime group structures Message-ID: References: <172437087178.59588.10818863865198159576.stgit@frogsfrogsfrogs> <172437087433.59588.10419191726395528458.stgit@frogsfrogsfrogs> <20240826191404.GC865349@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-xfs@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: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Aug 27, 2024 at 10:57:34AM +1000, Dave Chinner wrote: > We're discussing how to use the sparse fsbno addressing to allow > resizing of AGs, but we will not be able to do that at all with > rtgroups as they stand. The limitation is a 64 bit global rt extent > address is essential the physical address of the extent in the block > device LBA space. With this series there are not global RT extent addresses, the extents are always relative to the group and an entity only used in the allocator. > /* > * xfs_group - a contiguous 32 bit block address space group > */ > struct xfs_group { > struct xarray xarr; > u32 num_groups; > }; > > struct xfs_group_item { > struct xfs_group *group; /* so put/rele don't need any other context */ > u32 gno; > atomic_t passive_refs; > atomic_t active_refs; What is the point of splitting the group and group_item? This isn't done in the current perag struture either. > Hence I'm wondering if we should actually cap the maximum number of > rtgroups. WE're just about at BS > PS, so with a 64k block size a > single rtgroup can index 2^32 * 2^16 bytes which puts individual > rtgs at 256TB in size. Unless there are use cases for rtgroup sizes > smaller than a few GBs, I just don't see the need for support > theoretical maximum counts on tiny block size filesystems. Thirty > thousand rtgs at 256TB per rtg puts us at 64 bit device size limits, > and we hit those limits on 4kB block sizes at around 500,000 rtgs. > > So do we need to support millions of rtgs? I'd say no.... As said before hardware is having a word with with the 256GB hardware zone size in SMR HDDs. I hope that size will eventually increase, but I would not bet my house on it.