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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
=====================
@ -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