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docs/vm: split_page_table_lock: convert to ReST format

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Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mike Rapoport 2018-03-21 21:22:39 +02:00 committed by Jonathan Corbet
parent 0015190af2
commit d18edf52f4
1 changed files with 9 additions and 3 deletions
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12
Documentation/vm/split_page_table_lock
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@ -1,3 +1,6 @@
.. _split_page_table_lock:
=====================
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. tables. Access to higher level tables protected by mm->page_table_lock.
There are helpers to lock/unlock a table and other accessor functions: There are helpers to lock/unlock a table and other accessor functions:
- pte_offset_map_lock() - pte_offset_map_lock()
maps pte and takes PTE table lock, returns pointer to the taken maps pte and takes PTE table lock, returns pointer to the taken
lock; 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). tables and the architecture supports it (see below).
Hugetlb and split page table lock Hugetlb and split page table lock
--------------------------------- =================================
Hugetlb can support several page sizes. We use split lock only for PMD Hugetlb can support several page sizes. We use split lock only for PMD
level, but not for PUD. level, but not for PUD.
Hugetlb-specific helpers: Hugetlb-specific helpers:
- huge_pte_lock() - huge_pte_lock()
takes pmd split lock for PMD_SIZE page, mm->page_table_lock takes pmd split lock for PMD_SIZE page, mm->page_table_lock
otherwise; otherwise;
@ -47,7 +52,7 @@ Hugetlb-specific helpers:
returns pointer to table lock; returns pointer to table lock;
Support of split page table lock by an architecture Support of split page table lock by an architecture
--------------------------------------------------- ===================================================
There's no need in special enabling of PTE split page table lock: 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(), 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. be handled properly.
page->ptl page->ptl
--------- =========
page->ptl is used to access split page table lock, where 'page' is struct 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 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 To avoid increasing size of struct page and have best performance, we use a
trick: trick:
- if spinlock_t fits into long, we use page->ptr as spinlock, so we - if spinlock_t fits into long, we use page->ptr as spinlock, so we
can avoid indirect access and save a cache line. 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 - if size of spinlock_t is bigger then size of long, we use page->ptl as