[Cluster-devel] [GFS2 PATCH] GFS2: Speed up gfs2_rbm_from_block
Steven Whitehouse
swhiteho at redhat.com
Thu Oct 18 13:16:44 UTC 2012
Hi,
On Wed, 2012-10-17 at 11:06 -0400, Bob Peterson wrote:
> Hi,
>
> This patch is a rewrite of function gfs2_rbm_from_block. Rather than
> looping to find the right bitmap, the code now does a few simple
> math calculations. This speeds up the function significantly.
>
It would be a good plan to include the timings that you showed me
yesterday in the patch description to show the improvement this gives.
> Regards,
>
> Bob Peterson
> Red Hat File Systems
>
> Signed-off-by: Bob Peterson <rpeterso at redhat.com>
> ---
> diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
> index 3d469d3..24bb0b8 100644
> --- a/fs/gfs2/incore.h
> +++ b/fs/gfs2/incore.h
> @@ -621,6 +621,7 @@ struct gfs2_sbd {
> u32 sd_hash_bsize_shift;
> u32 sd_hash_ptrs; /* Number of pointers in a hash block */
> u32 sd_qc_per_block;
> + u32 sd_blocks_per_bitmap;
> u32 sd_max_dirres; /* Max blocks needed to add a directory entry */
> u32 sd_max_height; /* Max height of a file's metadata tree */
> u64 sd_heightsize[GFS2_MAX_META_HEIGHT + 1];
> diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
> index e443966..0e3554e 100644
> --- a/fs/gfs2/ops_fstype.c
> +++ b/fs/gfs2/ops_fstype.c
> @@ -278,6 +278,9 @@ static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent)
> sdp->sd_qc_per_block = (sdp->sd_sb.sb_bsize -
> sizeof(struct gfs2_meta_header)) /
> sizeof(struct gfs2_quota_change);
> + sdp->sd_blocks_per_bitmap = (sdp->sd_sb.sb_bsize -
> + sizeof(struct gfs2_meta_header))
> + * GFS2_NBBY; /* not the rgrp bitmap, subsequent bitmaps only */
>
> /* Compute maximum reservation required to add a entry to a directory */
>
> diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
> index 43d1a20..7635500 100644
> --- a/fs/gfs2/rgrp.c
> +++ b/fs/gfs2/rgrp.c
> @@ -250,23 +250,23 @@ static u32 gfs2_bitfit(const u8 *buf, const unsigned int len,
>
> static int gfs2_rbm_from_block(struct gfs2_rbm *rbm, u64 block)
> {
> - u64 rblock = block - rbm->rgd->rd_data0;
> - u32 goal = (u32)rblock;
> - int x;
> + u32 x;
>
> - if (WARN_ON_ONCE(rblock > UINT_MAX))
> - return -EINVAL;
This test was intended to check for underflow, i.e. that the block
number was less than rd_data0. I think it would be a good plan to retain
such a test even though we should not see any blocks outside of the
current bitmap.
Otherwise, it looks good,
Steve.
> if (block >= rbm->rgd->rd_data0 + rbm->rgd->rd_data)
> return -E2BIG;
>
> - for (x = 0; x < rbm->rgd->rd_length; x++) {
> - rbm->bi = rbm->rgd->rd_bits + x;
> - if (goal < (rbm->bi->bi_start + rbm->bi->bi_len) * GFS2_NBBY) {
> - rbm->offset = goal - (rbm->bi->bi_start * GFS2_NBBY);
> - break;
> - }
> - }
> + rbm->bi = rbm->rgd->rd_bits;
> + rbm->offset = (u32)(block - rbm->rgd->rd_data0);
> + /* Check if the block is within the first block */
> + if (rbm->offset < (rbm->bi->bi_start + rbm->bi->bi_len) * GFS2_NBBY)
> + return 0;
>
> + /* Adjust for the size diff between gfs2_meta_header and gfs2_rgrp */
> + rbm->offset += (sizeof(struct gfs2_rgrp) -
> + sizeof(struct gfs2_meta_header)) * GFS2_NBBY;
> + x = rbm->offset / rbm->rgd->rd_sbd->sd_blocks_per_bitmap;
> + rbm->offset -= x * rbm->rgd->rd_sbd->sd_blocks_per_bitmap;
> + rbm->bi += x;
> return 0;
> }
>
>
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