On Fri, Aug 25, 2017 at 12:18:42PM +0300, Timofey Titovets wrote:
> Copy sample data from input data range to sample buffer
> then calculate byte type count for that sample into bucket.
>
> Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
> ---
> fs/btrfs/heuristic.c | 38 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/heuristic.c b/fs/btrfs/heuristic.c
> index e3924c87af08..5192e51ab81e 100644
> --- a/fs/btrfs/heuristic.c
> +++ b/fs/btrfs/heuristic.c
> @@ -69,8 +69,20 @@ static struct list_head *heuristic_alloc_workspace(void)
> static int heuristic(struct list_head *ws, struct inode *inode,
> u64 start, u64 end)
> {
> + struct workspace *workspace = list_entry(ws, struct workspace, list);
> struct page *page;
> u64 index, index_end;
> + u32 a, b;
Please use more descriptive variable names. Using 'i' for simple
iteration is ok.
> + u8 *in_data, *sample = workspace->sample;
> + u8 byte;
> +
> + /*
> + * Compression only handle first 128kb of input range
> + * And just shift over range in loop for compressing it.
> + * Let's do the same.
> + */
> + if (end - start > BTRFS_MAX_UNCOMPRESSED)
> + end = start + BTRFS_MAX_UNCOMPRESSED;
>
> index = start >> PAGE_SHIFT;
> index_end = end >> PAGE_SHIFT;
> @@ -79,13 +91,37 @@ static int heuristic(struct list_head *ws, struct inode *inode,
> if (!IS_ALIGNED(end, PAGE_SIZE))
> index_end++;
>
> + b = 0;
> for (; index < index_end; index++) {
> page = find_get_page(inode->i_mapping, index);
> - kmap(page);
> + in_data = kmap(page);
> + /* Handle case where start unaligned to PAGE_SIZE */
> + a = start%PAGE_SIZE;
a = start % PAGE_SIZE;
> + while (a < PAGE_SIZE - READ_SIZE) {
> + /* Prevent sample overflow */
> + if (b >= MAX_SAMPLE_SIZE)
> + break;
> + /* Don't sample mem trash from last page */
> + if (start > end - READ_SIZE)
> + break;
I think you can merge the two conditions into one, if you calculate
beforehand where b would overflow 'end -> READ_SIZE'.
> + memcpy(&sample[b], &in_data[a], READ_SIZE);
> + a += ITER_SHIFT;
> + start += ITER_SHIFT;
> + b += READ_SIZE;
> + }
> kunmap(page);
> put_page(page);
> }
>
> + workspace->sample_size = b;
> +
> + memset(workspace->bucket, 0, sizeof(*workspace->bucket)*BUCKET_SIZE);
> +
> + for (a = 0; a < workspace->sample_size; a++) {
> + byte = sample[a];
> + workspace->bucket[byte].count++;
> + }
> +
> return 1;
> }
>
> --
> 2.14.1
> --
> 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
--
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
