04:18, Josef Bacik wrote:
> We have been creating bitmaps for small extents unconditionally forever. This
> was great when testing to make sure the bitmap stuff was working, but is
> overkill normally. So instead of always adding small chunks of free space to
> bitmaps, only start doing it if we go past half of our extent threshold. This
> will keeps us from creating a bitmap for just one small free extent at the front
> of the block group, and will make the allocator a little faster as a result.
> Thanks,
>
I was wondering this strategy when reading the code, so this patch
looks good to me.
Just a small nit:
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
> fs/btrfs/free-space-cache.c | 19 ++++++++++++++++---
> 1 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index 63776ae..7a808d7 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -1287,9 +1287,22 @@ static int insert_into_bitmap(struct btrfs_block_group_cache *block_group,
> * If we are below the extents threshold then we can add this as an
> * extent, and don't have to deal with the bitmap
> */
> - if (block_group->free_extents < block_group->extents_thresh &&
> - info->bytes > block_group->sectorsize * 4)
> - return 0;
> + if (block_group->free_extents < block_group->extents_thresh) {
> + /*
> + * If this block group has some small extents we don't want to
> + * use up all of our free slots in the cache with them, we want
> + * to reserve them to larger extents, however if we have plent
> + * of cache left then go ahead an dadd them, no sense in adding
> + * the overhead of a bitmap if we don't have to.
> + */
> + if (info->bytes < block_group->sectorsize * 4) {
This also changes how we define a small extent (from 4 sectorsize to 3).
Is it intended?
> + if ((block_group->free_extents * 2) <=
The parentheses isn't necessary nor help in readability I think.
> + block_group->extents_thresh)
> + return 0;
> + } else {
> + return 0;
> + }
> + }
>
> /*
> * some block groups are so tiny they can't be enveloped by a bitmap, so
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
