On Mon, Oct 13, 2008 at 11:12:25PM -0400, Theodore Tso wrote:
> On Mon, Oct 13, 2008 at 03:54:06PM -0400, Theodore Tso wrote:
> > So we have two choices; one is that we change ext4_mb_free_metadata()
> > to break up freed extents into block group chunks,
>
> Never mind. I took a closer look and realized that
> ext4_mb_free_blocks is already breaking up extents that span multiple
> block groups.
>
> So the only thing we need is the change to avoid merging freed extents
> that cross block groups, per my patch. I've updated the patch queue
> with such a fix so I can better test things out.
>
> Aneesh, can you look and see if this makes sense?
Yes the patch looks fine. Some changes I made on top of this is below
I have sent the patch -V5 with the above changes
>
> - Ted
>
> ext4: Use an rbtree for tracking blocks freed during transaction.
>
> From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>
> With this patch we track the block freed during a transaction using
> rb tree. We also make sure contiguous blocks freed are collected
> in one rb node.
>
.......
>
> +/*
> + * We can merge two free data extents of the physical blocks
s/of the/only if the/
> + * are contiguous, AND the extents were freed by the same transaction,
> + * AND the blocks are associated with the same group.
> + */
> +static int can_merge(struct ext4_free_data *entry1,
> + struct ext4_free_data *entry2)
> +{
> + if ((entry1->t_tid == entry2->t_tid) &&
> + (entry1->group == entry2->group) &&
> + (entry1->start_blk + entry1->count) == entry2->start_blk)
> + return 1;
> + return 0;
> +}
> +
......
> +++ b/fs/ext4/mballoc.h
> @@ -98,23 +98,34 @@
>
> static struct kmem_cache *ext4_pspace_cachep;
> static struct kmem_cache *ext4_ac_cachep;
> +static struct kmem_cache *ext4_free_ext_cachep;
>
> #ifdef EXT4_BB_MAX_BLOCKS
> #undef EXT4_BB_MAX_BLOCKS
> #endif
> #define EXT4_BB_MAX_BLOCKS 30
>
We don't need the above define.
> -struct ext4_free_metadata {
> - ext4_group_t group;
> - unsigned short num;
> - ext4_grpblk_t blocks[EXT4_BB_MAX_BLOCKS];
> +struct ext4_free_data {
> + /* this links the free block information from group_info */
> + struct rb_node node;
> +
> + /* this links the free block information from ext4_sb_info */
> struct list_head list;
> +
> + /* group which free block extent belongs */
> + ext4_group_t group;
> +
> + /* free block extent */
> + ext4_grpblk_t start_blk;
> + ext4_grpblk_t count;
> +
> + /* transaction which freed this extent */
> + tid_t t_tid;
> };
>
> struct ext4_group_info {
> unsigned long bb_state;
> - unsigned long bb_tid;
> - struct ext4_free_metadata *bb_md_cur;
> + struct rb_root bb_free_root;
> unsigned short bb_first_free;
> unsigned short bb_free;
> unsigned short bb_fragments;
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