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 CB44D2980AA; Tue, 4 Mar 2025 17:17:13 +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=1741108635; cv=none; b=ujBCBQ8ZeFtLQlt+loMuvqhfh0CqDN2PgGsKe9oe3Hl3uu2qJnfatz2V1fFv8RbKIaWvZumoTeJPn0UzulEX5rqAU2OBKppxg40T/ifenAnA+qjA9275U6Mbeg4zinBLB4kSZjWR50QWykfjCEdrNhpNBNLoJPeA2BZSlP3bBAQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741108635; c=relaxed/simple; bh=3j+Qz7hT1f8OqjlZi9V6ZuZnjswQjZpLuYZfWeHW7K0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m/4yRG67kmhqTCvzfpmwGhglmLr36cdlkXDDrXnZ/G1zzwXzVz5cdh3IMr4V2aDXkzPpuZGlNqYZYsxlK0RDyChdnxDyFkhCLiTOhaRqzhgWkHag4mwpnmXIWQ/AAETwzhsvsNzZrmGLsUd1wWwykiWi4D3fMON2+kzp+9rZG9c= 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=JFrjF+sp; 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="JFrjF+sp" 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=/Uoeevh/Cjq7NLA2NMtRTv1MiqPIpGJ85FyoLQLLraE=; b=JFrjF+spdHGmhMsTnV97EVwxcB gjRe0ezJfT9DhgQSvu6I6A0PLsl1Or6kFvAcoqmV++vCFw8QSzX5HfwYf4BRNzlGzd8K7QhYvoguP S3EV7klTjp15oLbLbgFQ+kMoTwBbDCt0FXmIJPAtI9TrYx2DKRiT5uFxyAo/ex95NPXiArHu1KkGJ cT3EcJzKvfkr3mtqYCpWUtjNOUN/s2moR7tD1xvTZzHzHkr4I6sk8K1TSTdwH6NVKPoBMM4KJ27zV h12RaE3NFg3pSkoYDJV4J3uk3K43b50EXrqTlvmOmcV6QBhoNYmm4NrWtHzBfdwBw2VpdgRnUH7a0 /YQfRolQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tpVtH-00000005ahU-2jq2; Tue, 04 Mar 2025 17:17:11 +0000 Date: Tue, 4 Mar 2025 09:17:11 -0800 From: Christoph Hellwig To: Heinz Mauelshagen Cc: Christoph Hellwig , Mikulas Patocka , Jens Axboe , Jooyung Han , Alasdair Kergon , Mike Snitzer , zkabelac@redhat.com, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] the dm-loop target Message-ID: References: <7d6ae2c9-df8e-50d0-7ad6-b787cb3cfab4@redhat.com> <8adb8df2-0c75-592d-bc3e-5609bb8de8d8@redhat.com> 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: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Mar 04, 2025 at 06:01:04PM +0100, Heinz Mauelshagen wrote: > > As Mikulas shared earlier: > > The Android people concluded that loop is too slow and rather than using > > loop they want to map a file using a table with dm-linear targets over the > > image of the host filesystem. So, they are already doing what dm-loop is > > doing. Which again is completely handwavy. What is the workload. What are the issues with the workload? Where is the time spent making it slower. e.g. the extent mapping code in this patch is a lot less efficient than the btree based extent lookup in XFS. If it is faster it is not looking up the extents but something else, and you need to figure out what it is.