struct ext4_inode_info embeds struct inode, but ext4_inode_cache does not request cache-line alignment. On the tested x86-64 build, struct ext4_inode_info is 1072 bytes, so consecutive objects can start at different offsets within a 64-byte cache line. The embedded inode starts at offset 232, with i_ctime_nsec, i_blkbits, i_state, and i_rwsem at offsets 352, 366, 376, and 384, respectively. When the containing object is not cache-line aligned, inode metadata and i_rwsem can occupy the same cache line. Metadata updates then invalidate the line used by CPUs contending on i_rwsem. Add SLAB_HWCACHE_ALIGN to ext4_inode_cache. This makes the containing objects start at cache-line boundaries and, with the tested layout, places i_rwsem at the start of a cache line separate from the preceding metadata. Tests were run on Linux 7.2 on a two-socket Intel Xeon Silver 4208 system with 16 CPUs, SMT disabled, and the frequency fixed at 2 GHz. Ten normal-mode runs of each zjhbench workload gave: before after change unixbench.fstime 488330.6 543996.2 +11.40% unixbench.fsdisk 1396385.0 1501352.5 +7.52% On this build, the slab allocation size grows from 1072 to 1088 bytes, an increase of 16 bytes (1.49%) per ext4 inode. RFC questions: 1. Is using SLAB_HWCACHE_ALIGN for ext4_inode_cache acceptable when the measured benefit depends on the current struct inode layout? 2. Would it be preferable to enable the alignment only when vfs_inode.i_rwsem is naturally cache-line aligned within struct ext4_inode_info, rather than enabling it unconditionally? 3. Should this false sharing instead be addressed in the generic VFS inode layout, despite the significantly larger memory and cross-filesystem impact? 4. What additional workloads or configuration coverage would be required before this could be considered as a non-RFC patch? Link: https://lore.kernel.org/linux-fsdevel/CAGudoHFgtM8Px4mRNM_fsmi3=vAyCMPC3FBCzk5uE7ma7fdbdQ@mail.gmail.com/ Signed-off-by: JonasZhou --- fs/ext4/super.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 245f67d10ded..11090fca1613 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1510,7 +1510,8 @@ static int __init init_inodecache(void) ext4_inode_cachep = kmem_cache_create("ext4_inode_cache", sizeof(struct ext4_inode_info), &args, - SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT); + SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT | + SLAB_HWCACHE_ALIGN); if (ext4_inode_cachep == NULL) return -ENOMEM; -- 2.43.0