Amir Goldstein
99c228a994
Kernel test robot reported [1] a 6% performance regression in a concurrent unlink(2) workload on commit60f7ed8c7c("fsnotify: send path type events to group with super block marks"). The performance test was run with no fsnotify marks at all on the data set, so the only extra instructions added by the offending commit are tests of the super_block fields s_fsnotify_{marks,mask} and these tests happen on almost every single inode access. When adding those fields to the super_block struct, we did not give much thought of placing them on a hot cache lines (we just placed them at the end of the struct). Re-organize struct super_block to try and keep some frequently accessed fields on the same cache line. Move the frequently accessed fields s_fsnotify_{marks,mask} near the frequently accessed fields s_fs_info,s_time_gran, while filling a 64bit alignment hole after s_time_gran. Move the seldom accessed fields s_id,s_uuid,s_max_links,s_mode near the seldom accessed fields s_vfs_rename_mutex,s_subtype. Rong Chen confirmed that this patch solved the reported problem. [1] https://lkml.org/lkml/2018/9/30/206 Reported-by: kernel test robot <rong.a.chen@intel.com> Tested-by: kernel test robot <rong.a.chen@intel.com> Fixes:1e6cb72399("fsnotify: add super block object type") Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
Linux kernel
============
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