From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
This series does not attempt any grand restructuring as I proposed last
week. Instead, it cures the worst of the indentitis, fixes the
documentation and reduces the ifdeffery. The only layout change is
compound_dtor and compound_order are each reduced to one byte. At
least, that's my intent.
Here's a diff from pahole's output:
--- old-struct-page 2017-12-16 09:58:09.653936791 -0500
+++ new-struct-page 2017-12-16 09:58:32.009832964 -0500
@@ -11,17 +11,15 @@
}; /* 16 8 */
union {
long unsigned int counters; /* 8 */
+ unsigned int active; /* 4 */
struct {
- union {
- atomic_t _mapcount; /* 4 */
- unsigned int active; /* 4 */
- struct {
- unsigned int inuse:16; /* 24:16 4 */
- unsigned int objects:15; /* 24: 1 4 */
- unsigned int frozen:1; /* 24: 0 4 */
- }; /* 4 */
- int units; /* 4 */
- }; /* 24 4 */
+ unsigned int inuse:16; /* 24:16 4 */
+ unsigned int objects:15; /* 24: 1 4 */
+ unsigned int frozen:1; /* 24: 0 4 */
+ }; /* 4 */
+ int units; /* 4 */
+ struct {
+ atomic_t _mapcount; /* 24 4 */
atomic_t _refcount; /* 28 4 */
}; /* 8 */
}; /* 24 8 */
@@ -36,8 +34,8 @@
struct callback_head callback_head; /* 16 */
struct {
long unsigned int compound_head; /* 32 8 */
- unsigned int compound_dtor; /* 40 4 */
- unsigned int compound_order; /* 44 4 */
+ unsigned char compound_dtor; /* 40 1 */
+ unsigned char compound_order; /* 41 1 */
}; /* 16 */
struct {
long unsigned int __pad; /* 32 8 */
Matthew Wilcox (8):
mm: Align struct page more aesthetically
mm: De-indent struct page
mm: Remove misleading alignment claims
mm: Improve comment on page->mapping
mm: Introduce _slub_counter_t
mm: Store compound_dtor / compound_order as bytes
mm: Document how to use struct page
mm: Remove reference to PG_buddy
include/linux/mm_types.h | 153 ++++++++++++++++++++++-------------------------
1 file changed, 73 insertions(+), 80 deletions(-)
--
2.15.1
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