Commit 06357b79 authored by Yang Yingliang's avatar Yang Yingliang Committed by Zeng Heng
Browse files

ext4: mitigatin cacheline false sharing in struct ext4_inode_info 

hulk inclusion
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/I8J122



--------------------------------

In the test of execl, shell1 and shell8 of UnixBench, L3 false sharing
occurs between rwsem_try_write_lock_unqueued() and filemap_map_pages().

The offset between address_space.host and address_space.i_mmap_rwsem
is 48. It may occur L3 false sharing. Their offsets in struct ext4_inode_info
is 696 and 744, so when the address of ext4_inode_info after L3 aligned,
it may occur L3 false sharing in the following condition:

[0x00 ~ 0x10] false sharing
[0x18 ~ 0x40] no false sharing
[0x48 ~ 0x80] false sharing

Change the offset of 'vfs_inode' from 320 to 360 in ext4_inode_info and
make the address of ext4_inode_info L3 aligned, so the offset of host
and i_mmap_rwsem in ext4_inode_info is changed to 736 and 784, it can
make them in different L3 to avoid false sharing.

./Run -c 96 -i 3 execl

Before this patch:
System Benchmarks Partial Index              BASELINE       RESULT    INDEX
Execl Throughput                                 43.0      24238.0   5636.8
                                                                   ========
System Benchmarks Index Score (Partial Only)                         5636.8

After this patch:
System Benchmarks Partial Index              BASELINE       RESULT    INDEX
Execl Throughput                                 43.0      29363.7   6828.8
                                                                   ========
System Benchmarks Index Score (Partial Only)                         6828.8

Signed-off-by: default avatarYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: default avatarZeng Heng <zengheng4@huawei.com>
parent 3871a15b

fs/ext4/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -125,3 +125,12 @@ config EXT4_ERROR_REPORT 
	help

	  Implement the ext3/ext4 file system error report. Report error to

	  userspace by netlink



config EXT4_MITIGATION_FALSE_SHARING

	bool "mitigation false sharing in ext4 inode"

	depends on EXT4_FS

	default n

	help

	  Enable this to mitigation cacheline false sharing in ext4 inode info.



	  If unsure, say N.

fs/ext4/ext4.h

+5 −0
Original line number Diff line number Diff line
@@ -1092,7 +1092,9 @@ struct ext4_inode_info { 
	 * to occasionally drop it.

	 */

	struct rw_semaphore i_mmap_sem;

#ifndef CONFIG_EXT4_MITIGATION_FALSE_SHARING

	struct inode vfs_inode;

#endif

	struct jbd2_inode *jinode;



	spinlock_t i_raw_lock;	/* protects updates to the raw inode */
@@ -1105,6 +1107,9 @@ struct ext4_inode_info { 


	/* mballoc */

	atomic_t i_prealloc_active;

#ifdef CONFIG_EXT4_MITIGATION_FALSE_SHARING

	struct inode vfs_inode;

#endif

	struct list_head i_prealloc_list;

	spinlock_t i_prealloc_lock;

fs/ext4/super.c

+4 −0
Original line number Diff line number Diff line
@@ -1436,7 +1436,11 @@ static void init_once(void *foo) 
static int __init init_inodecache(void)

{

	ext4_inode_cachep = kmem_cache_create_usercopy("ext4_inode_cache",

#ifdef CONFIG_EXT4_MITIGATION_FALSE_SHARING

				sizeof(struct ext4_inode_info), 128,

#else

				sizeof(struct ext4_inode_info), 0,

#endif

				(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|

					SLAB_ACCOUNT),

				offsetof(struct ext4_inode_info, i_data),