From patchwork Tue Jun 29 02:42:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12349247 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD123C11F65 for ; Tue, 29 Jun 2021 02:43:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8309961D19 for ; Tue, 29 Jun 2021 02:43:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8309961D19 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D9A4C8D012F; Mon, 28 Jun 2021 22:43:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D4AA98D00F0; Mon, 28 Jun 2021 22:43:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C119B8D012F; Mon, 28 Jun 2021 22:43:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0204.hostedemail.com [216.40.44.204]) by kanga.kvack.org (Postfix) with ESMTP id 9580B8D00F0 for ; Mon, 28 Jun 2021 22:43:00 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 94F598249980 for ; Tue, 29 Jun 2021 02:43:00 +0000 (UTC) X-FDA: 78305214120.12.E2DBAF2 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf27.hostedemail.com (Postfix) with ESMTP id 36B238019378 for ; Tue, 29 Jun 2021 02:43:00 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 1CC8361D15; Tue, 29 Jun 2021 02:42:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1624934579; bh=Spq5HFi2QYGnOvZh7jJs+2C16SStqFyULlu3H7ZLsdA=; h=Date:From:To:Subject:In-Reply-To:From; b=TzvZ92LHIDDaHsbQ5d8dl17c6ZzM7tyLpYNO73JCpAnkxszWKchA5WQxQ1NEy36lC gb6RhlZt9LWVqmacgrCOgAc5R6KMiTwWCs+2elF4/ZPM21AKQoW2uREjYGGV89tnst g7MCkfPWeduQMzyL2L/NKpoVeQsOjvSLSw0ifPZI= Date: Mon, 28 Jun 2021 19:42:58 -0700 From: Andrew Morton To: akpm@linux-foundation.org, arnd@arndb.de, corbet@lwn.net, david@redhat.com, geert@linux-m68k.org, ink@jurassic.park.msu.ru, linux-mm@kvack.org, mattst88@gmail.com, mm-commits@vger.kernel.org, rppt@linux.ibm.com, rth@twiddle.net, torvalds@linux-foundation.org, vgupta@synopsys.com Subject: [patch 186/192] docs: remove description of DISCONTIGMEM Message-ID: <20210629024258.gwGvwD9it%akpm@linux-foundation.org> In-Reply-To: <20210628193256.008961950a714730751c1423@linux-foundation.org> User-Agent: s-nail v14.8.16 Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=TzvZ92LH; spf=pass (imf27.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: djjocimo4iy8iomqqg3eu4eu5uxo7a6e X-Rspamd-Queue-Id: 36B238019378 X-Rspamd-Server: rspam06 X-HE-Tag: 1624934580-674612 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: From: Mike Rapoport Subject: docs: remove description of DISCONTIGMEM Remove description of DISCONTIGMEM from the "Memory Models" document and update VM sysctl description so that it won't mention DISCONIGMEM. Link: https://lkml.kernel.org/r/20210608091316.3622-8-rppt@kernel.org Signed-off-by: Mike Rapoport Acked-by: Arnd Bergmann Reviewed-by: David Hildenbrand Cc: Geert Uytterhoeven Cc: Ivan Kokshaysky Cc: Jonathan Corbet Cc: Matt Turner Cc: Richard Henderson Cc: Vineet Gupta Signed-off-by: Andrew Morton --- Documentation/admin-guide/sysctl/vm.rst | 12 ++--- Documentation/vm/memory-model.rst | 45 ---------------------- 2 files changed, 8 insertions(+), 49 deletions(-) --- a/Documentation/admin-guide/sysctl/vm.rst~docs-remove-description-of-discontigmem +++ a/Documentation/admin-guide/sysctl/vm.rst @@ -938,12 +938,12 @@ allocations, THP and hugetlbfs pages. To make it sensible with respect to the watermark_scale_factor parameter, the unit is in fractions of 10,000. The default value of -15,000 on !DISCONTIGMEM configurations means that up to 150% of the high -watermark will be reclaimed in the event of a pageblock being mixed due -to fragmentation. The level of reclaim is determined by the number of -fragmentation events that occurred in the recent past. If this value is -smaller than a pageblock then a pageblocks worth of pages will be reclaimed -(e.g. 2MB on 64-bit x86). A boost factor of 0 will disable the feature. +15,000 means that up to 150% of the high watermark will be reclaimed in the +event of a pageblock being mixed due to fragmentation. The level of reclaim +is determined by the number of fragmentation events that occurred in the +recent past. If this value is smaller than a pageblock then a pageblocks +worth of pages will be reclaimed (e.g. 2MB on 64-bit x86). A boost factor +of 0 will disable the feature. watermark_scale_factor --- a/Documentation/vm/memory-model.rst~docs-remove-description-of-discontigmem +++ a/Documentation/vm/memory-model.rst @@ -14,15 +14,11 @@ for the CPU. Then there could be several completely distinct addresses. And, don't forget about NUMA, where different memory banks are attached to different CPUs. -Linux abstracts this diversity using one of the three memory models: -FLATMEM, DISCONTIGMEM and SPARSEMEM. Each architecture defines what +Linux abstracts this diversity using one of the two memory models: +FLATMEM and SPARSEMEM. Each architecture defines what memory models it supports, what the default memory model is and whether it is possible to manually override that default. -.. note:: - At time of this writing, DISCONTIGMEM is considered deprecated, - although it is still in use by several architectures. - All the memory models track the status of physical page frames using struct page arranged in one or more arrays. @@ -63,43 +59,6 @@ straightforward: `PFN - ARCH_PFN_OFFSET` The `ARCH_PFN_OFFSET` defines the first page frame number for systems with physical memory starting at address different from 0. -DISCONTIGMEM -============ - -The DISCONTIGMEM model treats the physical memory as a collection of -`nodes` similarly to how Linux NUMA support does. For each node Linux -constructs an independent memory management subsystem represented by -`struct pglist_data` (or `pg_data_t` for short). Among other -things, `pg_data_t` holds the `node_mem_map` array that maps -physical pages belonging to that node. The `node_start_pfn` field of -`pg_data_t` is the number of the first page frame belonging to that -node. - -The architecture setup code should call :c:func:`free_area_init_node` for -each node in the system to initialize the `pg_data_t` object and its -`node_mem_map`. - -Every `node_mem_map` behaves exactly as FLATMEM's `mem_map` - -every physical page frame in a node has a `struct page` entry in the -`node_mem_map` array. When DISCONTIGMEM is enabled, a portion of the -`flags` field of the `struct page` encodes the node number of the -node hosting that page. - -The conversion between a PFN and the `struct page` in the -DISCONTIGMEM model became slightly more complex as it has to determine -which node hosts the physical page and which `pg_data_t` object -holds the `struct page`. - -Architectures that support DISCONTIGMEM provide :c:func:`pfn_to_nid` -to convert PFN to the node number. The opposite conversion helper -:c:func:`page_to_nid` is generic as it uses the node number encoded in -page->flags. - -Once the node number is known, the PFN can be used to index -appropriate `node_mem_map` array to access the `struct page` and -the offset of the `struct page` from the `node_mem_map` plus -`node_start_pfn` is the PFN of that page. - SPARSEMEM =========