On Tue 12-04-16 18:54:46, Waiman Long wrote: > When many threads are trying to add or delete inode to or from > a superblock's s_inodes list, spinlock contention on the list can > become a performance bottleneck. > > This patch changes the s_inodes field to become a per-cpu list with > per-cpu spinlocks. As a result, the following superblock inode list > (sb->s_inodes) iteration functions in vfs are also being modified: > > 1. iterate_bdevs() > 2. drop_pagecache_sb() > 3. wait_sb_inodes() > 4. evict_inodes() > 5. invalidate_inodes() > 6. fsnotify_unmount_inodes() > 7. add_dquot_ref() > 8. remove_dquot_ref() > > With an exit microbenchmark that creates a large number of threads, > attachs many inodes to them and then exits. The runtimes of that > microbenchmark with 1000 threads before and after the patch on a > 4-socket Intel E7-4820 v3 system (40 cores, 80 threads) were as > follows: > > Kernel Elapsed Time System Time > ------ ------------ ----------- > Vanilla 4.5-rc4 65.29s 82m14s > Patched 4.5-rc4 22.81s 23m03s > > Before the patch, spinlock contention at the inode_sb_list_add() > function at the startup phase and the inode_sb_list_del() function at > the exit phase were about 79% and 93% of total CPU time respectively > (as measured by perf). After the patch, the percpu_list_add() > function consumed only about 0.04% of CPU time at startup phase. The > percpu_list_del() function consumed about 0.4% of CPU time at exit > phase. There were still some spinlock contention, but they happened > elsewhere. > > Signed-off-by: Waiman Long <Waiman.Long@xxxxxxx> The patch looks good to me. You can add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
