From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 A8F8412FB02; Tue, 2 Jul 2024 11:51:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719921119; cv=none; b=NGEPW+NTTz9b0hDbIp+crhLZk5WaudO8QDVnrTHqnD/Gk8PUk7Ld9R1Hdh87LY54CK6gogZmnd1xhmRxL7ZjlLDGNnEOC3NBzhT8F9G4fpL5Pu6rsm3rcGh1CxJ5SjCyOq4RTQQLKHQvqn5FKju7aR+lGQaUSvlaJ/AR4nWWz5A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719921119; c=relaxed/simple; bh=FEnpvishjCAzWVQUMT7jQW/jici2ageO5mrvsiNPeQg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KGSj8vJq1JG+zqDlMt3rjsFPRWQVjfvqwMymXPaE2z7IcXa3XPb54XOiJOna9P4kTnpYFTOVuM+qx3qleJwwzLxfliaGPY16mIGVjtAHYUVjKe/JMoCvWUmbEdL+PSZb6iVnt1dYKz0HplindFump3RkqFauzeI81Y92oGGG3/k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id D343968AA6; Tue, 2 Jul 2024 13:51:51 +0200 (CEST) Date: Tue, 2 Jul 2024 13:51:51 +0200 From: Christoph Hellwig To: Alistair Popple Cc: David Hildenbrand , dan.j.williams@intel.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com Subject: Re: [PATCH 07/13] huge_memory: Allow mappings of PUD sized pages Message-ID: <20240702115151.GA16313@lst.de> References: <874j98gjfg.fsf@nvdebian.thelocal> 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: <874j98gjfg.fsf@nvdebian.thelocal> User-Agent: Mutt/1.5.17 (2007-11-01) On Tue, Jul 02, 2024 at 08:19:01PM +1000, Alistair Popple wrote: > > (B) As long as we have subpage mapcounts, this prevents vmemmap > > optimizations [1]. Is that only used for device-dax for now and are > > there no plans to make use of that for fs-dax? > > I don't have any plans to. This is purely focussed on refcounting pages > "like normal" so we can get rid of all the DAX special casing. > > > (C) We managed without so far :) > > Indeed, although Christoph has asked repeatedly ([1], [2] and likely > others) that this gets fixed and I finally got sick of it coming up > everytime I need to touch something with ZONE_DEVICE pages :) > > Also it removes the need for people to understand the special DAX page > recounting scheme and ends up removing a bunch of cruft as a bonus: > > 59 files changed, 485 insertions(+), 869 deletions(-) > > And that's before I clean up all the pgmap reference handling. It also > removes the pXX_trans_huge and pXX_leaf distinction. So we managed, but > things could be better IMHO. Yes. I can't wait for this series making the finish line. There might be more chance for cleanups and optimizations around ZONE_DEVICE, but this alone is a huge step forward.