From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Mike Rapoport 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 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: 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