The major memory ussage in workqueue is on the pool_workqueue.
The pool_workqueue has alignment requirement which often leads
to padding.
Reducing the memory usage for the pool_workqueue is valuable.
And 32bit system often has less memory, less workqueues,
less works, less concurrent flush_workqueue()s, so we can
slash the flush color on 32bit system to reduce memory usage
Before patch:
The sizeof the struct pool_workqueue is 256 bytes,
only 136 bytes is in use in 32bit system
After patch:
The sizeof the struct pool_workqueue is 128 bytes,
only 104 bytes is in use in 32bit system, there is still
room for future usage.
Setting WORK_STRUCT_COLOR_BITS to 3 can't reduce the sizeof
the struct pool_workqueue in 64bit system, unless combined
with big refactor for unbound pwq.
Signed-off-by: Lai Jiangshan <la...@linux.alibaba.com>
---
include/linux/workqueue.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 26de0cae2a0a..c0f311926d01 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -39,7 +39,11 @@ enum {
WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */
#endif
+#if BITS_PER_LONG == 32
+ WORK_STRUCT_COLOR_BITS = 3,
+#else
WORK_STRUCT_COLOR_BITS = 4,
+#endif
WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT,
WORK_STRUCT_DELAYED = 1 << WORK_STRUCT_DELAYED_BIT,
@@ -65,6 +69,8 @@ enum {
* Reserve 8 bits off of pwq pointer w/ debugobjects turned off.
* This makes pwqs aligned to 256 bytes and allows 15 workqueue
* flush colors.
+ * For 32 bit system, the numbers are 7 bits, 128 bytes, 7 colors
+ * respectively.
*/
WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +
WORK_STRUCT_COLOR_BITS,
--
2.20.1
