From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E51D7C433EF for ; Tue, 23 Nov 2021 20:52:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5500D6B0072; Tue, 23 Nov 2021 15:51:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4D8726B0074; Tue, 23 Nov 2021 15:51:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 350F36B0075; Tue, 23 Nov 2021 15:51:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0232.hostedemail.com [216.40.44.232]) by kanga.kvack.org (Postfix) with ESMTP id 1F87E6B0072 for ; Tue, 23 Nov 2021 15:51:48 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id C44E1182D109B for ; Tue, 23 Nov 2021 20:51:37 +0000 (UTC) X-FDA: 78841391034.28.77615DD Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf17.hostedemail.com (Postfix) with ESMTP id B14AEF0001F6 for ; Tue, 23 Nov 2021 20:51:36 +0000 (UTC) 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=4VkUJFZfBikgHkbvPCTgubczW3p/ZjTIGcBnmCIkGFE=; b=td9GgBH3w0ndjVdL3WgxOIVa+5 NfglRythKi8YXAcNoDmURi3YmyUPYMS1I6SrvyElzur5JY50fe418qj0xPSpXt/gFXINy3+Y+OMxL bBc1yEmoTrRrN4jRdiO35d6pCMEGlT1j9fs5H60jYEqUj/zkk+MRuIFQRyK0TZNWxorcNtzFYl3Z9 jBBwBgpNtTOBxgfLV+j5SVpWUB1Hl8qnu9o2pDehmnA1hqW1i8isGWdsdlqPaBdQ5VVdOa/7hBFmR txqSv1CGZ/4yRKXxxRaU3zZpezR2TyZdOiv577qeuVaRzZ6Cp1odPe/K4sryaZPZ/1gRnknYuIyMV ZndgfYSQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mpcl7-00GMub-Hh; Tue, 23 Nov 2021 20:51:21 +0000 Date: Tue, 23 Nov 2021 20:51:21 +0000 From: Matthew Wilcox To: Mina Almasry Cc: Jonathan Corbet , David Hildenbrand , "Paul E . McKenney" , Yu Zhao , Andrew Morton , Peter Xu , Ivan Teterevkov , Florian Schmidt , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v7] mm: Add PM_THP_MAPPED to /proc/pid/pagemap Message-ID: References: <20211123000102.4052105-1-almasrymina@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211123000102.4052105-1-almasrymina@google.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B14AEF0001F6 X-Stat-Signature: jhjo8onprrwa1xggmp615xyatdx68rqw Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=td9GgBH3; dmarc=none; spf=none (imf17.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-HE-Tag: 1637700696-553833 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 22, 2021 at 04:01:02PM -0800, Mina Almasry wrote: > Add PM_THP_MAPPED MAPPING to allow userspace to detect whether a given virt > address is currently mapped by a transparent huge page or not. Example > use case is a process requesting THPs from the kernel (via a huge tmpfs > mount for example), for a performance critical region of memory. The > userspace may want to query whether the kernel is actually backing this > memory by hugepages or not. So you want this bit to be clear if the memory is backed by a hugetlb page? > if (page && page_mapcount(page) == 1) > flags |= PM_MMAP_EXCLUSIVE; > + if (page && is_transparent_hugepage(page)) > + flags |= PM_THP_MAPPED; because honestly i'd expect it to be more useful to mean "This memory is mapped by a PMD entry" and then the code would look like: if (page) flags |= PM_PMD_MAPPED; (and put a corresponding change in pagemap_hugetlb_range)