On 2023/3/10 14:35, Gao Xiang wrote:
On 2023/3/10 14:27, Yangtao Li wrote:
Please don't do this. This makes the code compile down to a division, which is
far less efficient. I've verified this by checking the assembly generated.
How much is the performance impact? So should the following be modified as shift operations as well?
fs/erofs/namei.c:92: int head = 0, back = DIV_ROUND_UP(dir->i_size, EROFS_BLKSIZ) - 1;
fs/erofs/zmap.c:252: const unsigned int totalidx = DIV_ROUND_UP(inode->i_size, EROFS_BLKSIZ);
fs/erofs/decompressor.c:14:#define LZ4_MAX_DISTANCE_PAGES (DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
fs/erofs/decompressor.c:56: DIV_ROUND_UP(distance, PAGE_SIZE) + 1 :
fs/erofs/decompressor.c:70: unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
fs/erofs/data.c:84: nblocks = DIV_ROUND_UP(inode->i_size, EROFS_BLKSIZ);
Please stop taking EROFS as example on ext4 patches
and they will all be changed due to subpage support.
Here EROFS_BLKSIZ == PAGE_SIZE is a constant, so no difference
to use shift or division.
Thx,
Yangtao
