On 03/22/2018 01:15 PM, Matthew Wilcox wrote:
On Tue, Mar 20, 2018 at 10:11:01PM +0800, Aaron Lu wrote:
A new document file called "struct_page_filed" is added to explain
the newly reused field in "struct page".
Sounds rather ad-hoc for a single field, I'd rather document it via
comments.
Dave would like to have a document to explain all those "struct page"
fields that are repurposed under different scenarios and this is the
very start of the document :-)
I probably should have explained the intent of the document more.
Dave and I are in agreement on "Shouldn't struct page be better documented".
I came up with this a few weeks ago; never quite got round to turning it
into a patch:
+---+-----------+-----------+--------------+----------+--------+--------------+
| B | slab | pagecache | tail 1 | anon | tail 1 | hugetlb |
+===+===========+===========+==============+==========+========+==============+
| 0 | flags |
+---+ |
| 4 | |
+---+-----------+-----------+--------------+----------+--------+--------------+
| 8 | s_mem | mapping | cmp_mapcount | anon_vma | defer | mapping |
+---+ | +--------------+ | list | |
|12 | | | | | | |
+---+-----------+-----------+--------------+----------+ +--------------+
|16 | freelist | index | | index |
+---+ | | | (shifted) |
|20 | | | | |
+---+-----------+-------------------------------------+--------+--------------+
|24 | counters | mapcount |
+---+ +-----------+--------------+----------+--------+--------------+
|28 | | refcount | | | | refcount |
+---+-----------+-----------+--------------+----------+--------+--------------+
|32 | next | lru | cmpd_head | | lru |
+---+ | | +-------------------+ +
|36 | | | | | |
+---+-----------+ +--------------+-------------------+ +
|40 | pages | | dtor / order | | |
+---+-----------+ +--------------+-------------------+ +
|44 | pobjects | | | | |
+---+-----------+-----------+--------------+----------------------------------+
|48 | slb_cache | private | | |
+---+ | +--------------+----------------------------------+
|52 | | | | |
+---+-----------+-----------+--------------+----------------------------------+
Shouldn't the anon column also contain lru?
