From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 7D1AA5811C for ; Thu, 14 Mar 2024 14:15:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710425759; cv=none; b=HZyx+V1hdDXPFzzpPhnAjtLVaUNsVppony7jioS26LsmZPtLPOTrPJRHNP8d3h3eCv0ol+siOs6ACGs89GsulrMe6A8ArBItUw+o4YnusBy8FRQquoZTg3p8mflUSbz4XlcLIW90sGmVTITcWc5m+WFI9kUwYNh5dGoA1PhCEMQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710425759; c=relaxed/simple; bh=M6667Wh2li32mzjwCOvp/fptR+/dW71OKBrRDGYVuiU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VY+WJrYTt/D2Fus2gJ8lIiYue2gSTJUXScRS6NZtaKsi8Vk5bzbJZpL/IYt11M2Vw1bKR5ZAc3HgW9BwcJ5PdcWBmbYTNlmXWydi8VfhFTHBbsXR0ovHUBBlKLnA+SWaSJhQqvICgp1GrE7dj02h41tbrwoRxoUzuFiLf2Dvt3c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=N1kusd6t; arc=none smtp.client-ip=90.155.50.34 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=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="N1kusd6t" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=w2R7s8qU3kXnWekYLwTAxzb3rS1apBQsRtsNFnXuR2M=; b=N1kusd6tXe9gkjSaKuUeJDBVs8 Lv2rA+JgMQU+Bzu1u9asTuYVB8tLfRDKKKvQsVKdpqz1Q7cm9rWE7k1fgfBVeH8wc5V2lsTV4hQBS BlsDX4L8FTzbhTjI8ROPpH28T/oQncPG+2x9mXQttkicKz4+5DLZ/8Maf5lWyfGQm2HbJTx1cZM5c Oesj3ImCD/zEmR0WQjqGizpS/aHxdnc5+5S63WGEnYz4fDfzkrE8ot2Wft1LiF796Sgp9tBC884wp MFpchma2MylzgJ1x3AppbW29TGkC3J6zP0je9a2Uq00jDqkEAQu+Jh93GcsnaJxXWJHTkmV7Slp+S t+Qg3A7Q==; Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rkls3-0000000806t-1Lnf; Thu, 14 Mar 2024 14:15:47 +0000 Date: Thu, 14 Mar 2024 14:15:47 +0000 From: Matthew Wilcox To: Hannes Reinecke Cc: Pankaj Raghav , Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org, Tetsuo Handa Subject: Re: brd in a memdesc world Message-ID: References: <886d8bde-e608-4e15-b13d-c891b4689b4f@suse.de> 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: <886d8bde-e608-4e15-b13d-c891b4689b4f@suse.de> On Thu, Mar 14, 2024 at 12:11:18PM +0100, Hannes Reinecke wrote: > On 3/13/24 19:28, Matthew Wilcox wrote: > > None of those things are needed for brd's uses. All brd needs is to > > be able to allocate, kmap and free chunks of memory. Unless there are > > plans to do more than this. > > The primary goal of my patchset is to make brd a test-bed for the LBS work; > devices with a sector size larger than 4k are really hard to come > by. But really, it's just a testbed, and I'm not sure whether there's > a need for that in the general audience. > I can resubmit if you want ... > > As for the memory overhead, I guess it only makes a noticable difference > when moving to hugepages, and have brd allocate hugepages only. > But that is future work for sure. As I said, this is talking about a memdesc future where struct page is a mere 8 bytes and most of its contents are reserved to the MM. At this point, there's no extra overhead to your patch, but there would be when we get there. So I don't think the folio conversion is necessary, but I think supporting larger sector sizes in brd is a worthwhile extension.