On Sat, 24 Nov 2012, Theodore Ts'o wrote:
> Date: Sat, 24 Nov 2012 19:36:30 -0500
> From: Theodore Ts'o <tytso@xxxxxxx>
> To: Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Subject: [PATCH 2/6] e2fsck: optimize pass1 for CPU time
>
> Optimize e2fsck pass 1 by marking entire extents as being in use at a
> time, instead of block by block. This optimization only works for
> non-bigalloc file systems for now (it's tricky to handle bigalloc file
> systems since this code is also responsible for dealing with blocks
> that are not correctly aligned within a cluster). When the
> optimization works, the CPU savings can be significant: up to two or
> three CPU minutes for a full 4T disk.
>
> Addresses-Google-Bug: #7534813
Looks good.
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> e2fsck/pass1.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index 78fbe8d..cc00e0f 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -1432,6 +1432,16 @@ static _INLINE_ void mark_block_used(e2fsck_t ctx, blk64_t block)
> }
> }
>
> +static _INLINE_ void mark_blocks_used(e2fsck_t ctx, blk64_t block,
> + unsigned int num)
> +{
> + if (ext2fs_test_block_bitmap_range2(ctx->block_found_map, block, num))
> + ext2fs_mark_block_bitmap_range2(ctx->block_found_map, block, num);
> + else
> + while (num--)
> + mark_block_used(ctx, block++);
> +}
> +
> /*
> * Adjust the extended attribute block's reference counts at the end
> * of pass 1, either by subtracting out references for EA blocks that
> @@ -1867,11 +1877,15 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
> goto failed_add_dir_block;
> }
> }
> + if (!ctx->fs->cluster_ratio_bits) {
> + mark_blocks_used(ctx, extent.e_pblk, extent.e_len);
> + pb->num_blocks += extent.e_len;
> + }
> for (blk = extent.e_pblk, blockcnt = extent.e_lblk, i = 0;
> i < extent.e_len;
> blk++, blockcnt++, i++) {
> - if (!(ctx->fs->cluster_ratio_bits &&
> - pb->previous_block &&
> + if (ctx->fs->cluster_ratio_bits &&
> + !(pb->previous_block &&
> (EXT2FS_B2C(ctx->fs, blk) ==
> EXT2FS_B2C(ctx->fs, pb->previous_block)) &&
> (blk & EXT2FS_CLUSTER_MASK(ctx->fs)) ==
>
--
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