On Dec 03, 2007 13:05 -0600, Jose R. Santos wrote:
> @@ -600,6 +600,7 @@ void ext4_free_blocks_sb(handle_t *handle, struct super_block *sb,
> ext4_grpblk_t group_freed;
> + ext4_group_t meta_group;
Please do not call these meta_groups. This already means something very
specific (i.e. desc_per_block groups) and using it for FLEX_BG is confusing.
One possibly desirable relation is if the FLEX_BG count is some integer or
power-of-two multiple of the metabg count. That would allow the FLEX_BG
code to share the same in-memory group struct as the mballoc code and save
on some memory overhead.
> + meta_group = ext4_meta_group(sbi, block_group);
> + spin_lock(&sbi->s_meta_groups[meta_group].meta_group_lock);
> + sbi->s_meta_groups[meta_group].free_inodes++;
> + if (is_directory)
> + sbi->s_meta_groups[meta_group].num_dirs--;
> + spin_unlock(&sbi->s_meta_groups[meta_group].meta_group_lock);
This can be as many as hundreds or thousands of spin locks. Why not use
the same hashed locking code as the group descriptors themselves?
spin_lock(sb_bgl_lock(sbi, meta_group));
spin_unlock(sb_bgl_lock(sbi, meta_group));
This scales with the number of CPUs and chance of contention is very low.
> +int find_group_meta(struct super_block *sb, struct inode *parent)
> +{
> + ext4_group_t parent_mgroup = parent_group / sbi->s_groups_per_meta;
This could use ext4_meta_group(sbi, parent_group)?
> +static inline ext4_group_t ext4_meta_group(struct ext4_sb_info *sbi,
> + ext4_group_t block_group)
> +{
> + return block_group/sbi->s_groups_per_meta;
> +}
It would be preferable to limit s_groups_per_meta to be a power-of-two
so that this can become a shift instead of a divide.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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