From: Lai Jiangshan <laijs@linux.alibaba.com>
To: linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@linux.alibaba.com>,
Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>
Subject: [PATCH 4/4] workqueue: slash half memory usage in 32bit system
Date: Mon, 1 Jun 2020 08:44:42 +0000 [thread overview]
Message-ID: <20200601084442.8284-5-laijs@linux.alibaba.com> (raw)
In-Reply-To: <20200601084442.8284-1-laijs@linux.alibaba.com>
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 <laijs@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
next prev parent reply other threads:[~2020-06-01 8:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-01 8:44 [PATCH 0/4] workqueue: reduce the sizeof pool_workqueue Lai Jiangshan
2020-06-01 8:44 ` [PATCH 1/4] workqueue: fix a piece of comment about reserved bits for work flags Lai Jiangshan
2020-06-01 8:44 ` [PATCH 2/4] workqueue: use BUILD_BUG_ON() for compile time test instead of WARN_ON() Lai Jiangshan
2020-06-01 15:08 ` Tejun Heo
2020-06-01 8:44 ` [PATCH 3/4] workqueue: add a BUILD_BUG_ON() to check the size of struct pool_workqueue Lai Jiangshan
2020-06-01 8:44 ` Lai Jiangshan [this message]
2020-06-01 15:07 ` [PATCH 4/4] workqueue: slash half memory usage in 32bit system Tejun Heo
2020-06-02 0:08 ` Lai Jiangshan
2020-06-02 16:18 ` Tejun Heo
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