On Fri, 2010-08-20 at 15:11 -0500, Eric Sandeen wrote: > Richard Kennedy wrote: > > Reorder structure ext4_inode_info to remove 16 bytes of alignment > > padding on 64 bit builds. This shrinks its size from 904 to 888 bytes > > with (CONFIG_EXT4_S_XATTR=y && CONFIG_QUOTA=n). > > > > This will allow this structure to use one fewer cache lines. > > > > Also change type of i_delalloc_reserved_flag to bool to better reflect > > its usage. > > > > compiled & tested on x86_64 > > > Looks good to me; there is still a bit of padding at the end: > > qsize_t i_reserved_quota; /* 864 8 */ > struct list_head i_completed_io_list; /* 872 16 */ > spinlock_t i_completed_io_lock; /* 888 4 */ > > /* XXX 4 bytes hole, try to pack */ > > /* --- cacheline 14 boundary (896 bytes) --- */ > ext4_io_end_t * cur_aio_dio; /* 896 8 */ > tid_t i_sync_tid; /* 904 4 */ > tid_t i_datasync_tid; /* 908 4 */ > > > but it wouldn't save a cacheline anyway... > > -Eric > Thanks Eric, yes there is padding but we don't have anything to fill the hole with :( If it becomes important to save space, i_state_flags seem to be unused in ext4 so we could possibly drop that. With my patch applied, under slub I'm getting one more object per slab in the ext4_inode_cache [2.6.35] 17 objects of 960 bytes -- 4 pages per slab [+patch] 18 objects of 896 bytes -- 4 pages per slab So I guess that is where most of the write test performance improvement came from. regards Richard -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
