From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f198.google.com (mail-qt0-f198.google.com [209.85.216.198]) by kanga.kvack.org (Postfix) with ESMTP id B92016B0273 for ; Wed, 21 Mar 2018 15:24:49 -0400 (EDT) Received: by mail-qt0-f198.google.com with SMTP id x35so3928075qtx.5 for ; Wed, 21 Mar 2018 12:24:49 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id s49si5159880qth.42.2018.03.21.12.24.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Mar 2018 12:24:48 -0700 (PDT) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w2LJN3VL119131 for ; Wed, 21 Mar 2018 15:24:48 -0400 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 2gut67sdyw-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Wed, 21 Mar 2018 15:24:47 -0400 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 21 Mar 2018 19:24:44 -0000 From: Mike Rapoport Subject: [PATCH 23/32] docs/vm: split_page_table_lock: convert to ReST format Date: Wed, 21 Mar 2018 21:22:39 +0200 In-Reply-To: <1521660168-14372-1-git-send-email-rppt@linux.vnet.ibm.com> References: <1521660168-14372-1-git-send-email-rppt@linux.vnet.ibm.com> Message-Id: <1521660168-14372-24-git-send-email-rppt@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jonathan Corbet Cc: Andrey Ryabinin , Richard Henderson , Ivan Kokshaysky , Matt Turner , Tony Luck , Fenghua Yu , Ralf Baechle , James Hogan , Michael Ellerman , Alexander Viro , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kasan-dev@googlegroups.com, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport Signed-off-by: Mike Rapoport --- Documentation/vm/split_page_table_lock | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/Documentation/vm/split_page_table_lock b/Documentation/vm/split_page_table_lock index 62842a8..889b00b 100644 --- a/Documentation/vm/split_page_table_lock +++ b/Documentation/vm/split_page_table_lock @@ -1,3 +1,6 @@ +.. _split_page_table_lock: + +===================== Split page table lock ===================== @@ -11,6 +14,7 @@ access to the table. At the moment we use split lock for PTE and PMD tables. Access to higher level tables protected by mm->page_table_lock. There are helpers to lock/unlock a table and other accessor functions: + - pte_offset_map_lock() maps pte and takes PTE table lock, returns pointer to the taken lock; @@ -34,12 +38,13 @@ Split page table lock for PMD tables is enabled, if it's enabled for PTE tables and the architecture supports it (see below). Hugetlb and split page table lock ---------------------------------- +================================= Hugetlb can support several page sizes. We use split lock only for PMD level, but not for PUD. Hugetlb-specific helpers: + - huge_pte_lock() takes pmd split lock for PMD_SIZE page, mm->page_table_lock otherwise; @@ -47,7 +52,7 @@ Hugetlb-specific helpers: returns pointer to table lock; Support of split page table lock by an architecture ---------------------------------------------------- +=================================================== There's no need in special enabling of PTE split page table lock: everything required is done by pgtable_page_ctor() and pgtable_page_dtor(), @@ -73,7 +78,7 @@ NOTE: pgtable_page_ctor() and pgtable_pmd_page_ctor() can fail -- it must be handled properly. page->ptl ---------- +========= page->ptl is used to access split page table lock, where 'page' is struct page of page containing the table. It shares storage with page->private @@ -81,6 +86,7 @@ page of page containing the table. It shares storage with page->private To avoid increasing size of struct page and have best performance, we use a trick: + - if spinlock_t fits into long, we use page->ptr as spinlock, so we can avoid indirect access and save a cache line. - if size of spinlock_t is bigger then size of long, we use page->ptl as -- 2.7.4