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 AE8552D248C; Tue, 14 Oct 2025 14:32:47 +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=1760452369; cv=none; b=L5LoAnaWrshWKkD4lNQa3Mv4zHzLmJh3Zaihmyzg51bxiqhIFRt2pNvcTyJhH1KQlC0Dk0X2JzvEmabP9U2duY0kkxWltZzhJTzn5a2z2nkKIBJ6Hf4AJ8UkCiKtl9xrFrJwy1Vo/iHLWjK9qQE0Eo2uSqkl6V/fBttQjlSxTxM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760452369; c=relaxed/simple; bh=oHAN/0DxWPNDDT78S8xHGvdeMdd39Ebo18SZ31HvRdw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dyW+wJs0nNLYXTAQfjd/CtFUVVDlXzkf0J/M4/aQsJLI8XYhWtwDqR2+kCNOxDL2tS+eo2ui6oerJhrHT3kmsaTxV24NF2Op/d9u3wdHZ02zNJff7KeFwIIzBNkAi7gU/+DG1KWGxgwpfkXUEMSt5C4B+9tWwwNpJXMlxFXpy9w= 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=gANwOdXe; 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="gANwOdXe" 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=0GqYhA2elC/r2rvCKhRwX+jvXdEIHrho/9mEfMhvs2g=; b=gANwOdXeFS4A8Uk10aaWilWR7d ySohtwrkya4BSFA9MNyJwI2SZVkT1JJHEAJ1YXe7UWprbY1XwtET/2V4R4oRn4GF67uKnvqNrQQpm yhej7D3Ampn9gV2sdpBOC//k6+7VCRkiUzXc9CAocGziSDmflGDKxlzctCPJMtuj1ame1R/WX62J3 /q00WWJeO563d2TrDkgqDV3wLGgpDguZTVQJuU95qNOMg6pvwsczOA0E/TTHHdN4VGFQz3RMBH5p7 s4BBoP6jBFf72/l5Iy/B7dE73hYHCsC/5tBuD4pR9oLkR5r5JzFIJiPt40JHliYisLm0SxqKtLxy/ LUkZzWEA==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8g4v-0000000CSAd-1Vaf; Tue, 14 Oct 2025 14:32:41 +0000 Date: Tue, 14 Oct 2025 15:32:41 +0100 From: Matthew Wilcox To: David Hildenbrand Cc: Wei Yang , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Andrew Morton , Tejun Heo , Zefan Li , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Jonathan Corbet , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Muchun Song , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn Subject: Re: [PATCH v3 20/20] mm: stop maintaining the per-page mapcount of large folios (CONFIG_NO_PAGE_MAPCOUNT) Message-ID: References: <20250303163014.1128035-1-david@redhat.com> <20250303163014.1128035-21-david@redhat.com> <20251014122335.dpyk5advbkioojnm@master> <71380b43-c23c-42b5-8aab-f158bb37bc75@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <71380b43-c23c-42b5-8aab-f158bb37bc75@redhat.com> On Tue, Oct 14, 2025 at 02:59:30PM +0200, David Hildenbrand wrote: > > As commit 349994cf61e6 mentioned, we don't support partially mapped PUD-sized > > folio yet. > > We do support partially mapped PUD-sized folios I think, but not anonymous > PUD-sized folios. I don't think so? The only mechanism I know of to allocate PUD-sized chunks of memory is hugetlb, and that doesn't permit partial mappings.