On 05/02/2017 02:54 AM, lixiubo@xxxxxxxxxxxxxxxxxxxx wrote: > From: Xiubo Li <lixiubo@xxxxxxxxxxxxxxxxxxxx> > > For the "struct tcmu_cmd_entry" in cmd area, the minimum size > will be sizeof(struct tcmu_cmd_entry) == 112 Bytes. And it could > fill about (sizeof(struct rsp) - sizeof(struct req)) / > sizeof(struct iovec) == 68 / 16 ~= 4 data regions(iov[4]) by > default. > > For most tcmu_cmds, the data block indexes allocated from the > data area will be continuous. And for the continuous blocks they > will be merged into the same region using only one iovec. For > the current code, it will always allocates the same number of > iovecs with blocks for each tcmu_cmd, and it will wastes much > memories. > > For example, when the block size is 4K and the DATA_OUT buffer > size is 64K, and the regions needed is less than 5(on my > environment is almost 99.7%). The current code will allocate > about 16 iovecs, and there will be (16 - 4) * sizeof(struct > iovec) = 192 Bytes cmd area memories wasted. > > Here adds two helpers to calculate the base size and full size > of the tcmu_cmd. And will recalculate them again when it make sure > how many iovs is needed before insert it to cmd area. > > Signed-off-by: Xiubo Li <lixiubo@xxxxxxxxxxxxxxxxxxxx> Looks ok to me. Thanks. Acked-by: Mike Christie <mchristi@xxxxxxxxxx>
