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 DA22F171AF for ; Tue, 27 Aug 2024 05:18:45 +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=1724735927; cv=none; b=OvcMbvYHI0CEB5wziCU+RJj794tKgb+ni7Ho1wELIJGsOYoZVzHwNemv86LWtD0AJ4bFP9BTPn99aajsxzF2H+7P5pNk23XMu3yD0HdtHxjDw3HnCyPCDD6LuJAyqV86KiZT9+hZKbC+bcn6BieneWaHQMdNJHPSDqpu5noShtM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724735927; c=relaxed/simple; bh=iuhENakpoJqoxLBZdI4r4RD8iLSrSq00yYmrUIf7DH8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=C6MhiMVrUuawAI0cX0+ca0rROW+tBUNUvSxfNd8+EkwQPlR35t08YIS/HsHVXpaJc82ZXiB3dAUuIWxXsAvEpKkMbwS0b7lLX+Z0aM40nmEfGf50NRRg068DxIPbSJg2dw+UZs2yDENLYGdYf88ifNs1G2f0EYbfWjsgVJ4Zbe0= 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=zCPWtasb; 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="zCPWtasb" 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=+P+UbMogebRzRtZA9m+fPseeXIGaZ8IhyvOo+TfWX18=; b=zCPWtasbmiu2IG+qWqpjSjWKwa RLevpNfWC1zoHqQVlTyK8/EiypBOH9hdaI2LtXv86nJZ8s0Bllt1My/UIUpAQe3T+Nmky+xNBPwsV SesQp1uVKdmhCoUIUtdphQDenc87+qMyLp3KHEAU5KY1onGWuff+Vy0TklpBshq+dD0Qn7x6U4YO4 sfenO0OREcVPYSwcQhYbHb9yuMvVIivDF2s4zG9oI5BnnARReM4LQbupDWwjN+rdM2NpEV9D9JJMi LnG4VfB0C4bvFxkX8LFcnEVbJE6Pi0HG6bQ4ysOqId5xVV2GEEJZedETkGilfK404UvvymGcZHGa1 qKBVoUpQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1siobN-00000009qV3-0Yhh; Tue, 27 Aug 2024 05:18:45 +0000 Date: Mon, 26 Aug 2024 22:18:45 -0700 From: Christoph Hellwig To: "Darrick J. Wong" Cc: Christoph Hellwig , Dave Chinner , 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> <20240827051719.GJ865349@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: <20240827051719.GJ865349@frogsfrogsfrogs> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Aug 26, 2024 at 10:17:19PM -0700, Darrick J. Wong wrote: > > 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. > > I think xfs_group encapsulates/replaces the radix tree root in struct > xfs_mount, and the xarray inside it points to xfs_group_item objects. Ahh. So it's now a xfs_group structure, but a xfs_groups one, with the group item really being xfs_group. > > > > 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. > > Wait, 256 *gigabytes*? That wouldn't be such a bad minimum. Sorry, MB. My units really suck this morning :)