On 9/3/24 4:54 AM, ZhangHui wrote:
Currently, for a controller that supports multiple queues, like UFS4.0, the mq_ops->complete is executed in the interrupt top-half. Therefore, the file system's end io is executed during the request completion process, such as f2fs_write_end_io on smartphone. However, we found that the execution time of the file system end io is strongly related to the size of the bio and the processing speed of the CPU. Because the file system's end io will traverse every page in bio, this is a very time-consuming operation. We measured that the 80M bio write operation on the little CPU will cause the execution time of the top-half to be greater than 100ms. The CPU tick on a smartphone is only 4ms, which will undoubtedly affect scheduling efficiency. Let's fixed this issue by moved non sync request completion flow to softirq, and keep the sync request completion in the top-half.
An explanation is missing from the patch description why this issue cannot be solved by changing rq_affinity to 2. Thanks, Bart.
