On 2024/9/7 21:46, Jens Axboe wrote: > On 9/6/24 8:49 PM, ZhangHui wrote: >> From: zhanghui <zhanghui31@xxxxxxxxxx> >> >> 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, >> which will undoubtedly affect interrupt response latency. >> >> Let's fix this issue by moving non sync requests completion to softirq >> context, and keeping sync requests completion in the IRQ top-half context. > You keep ignoring the feedback, and hence I too shall be ignoring this > patch going forward then. > > The key issue here is that the completion takes so long, and adding a > heuristic that equates not-sync with latency-not-important is pretty > bogus and not a good way to attempt to work around it. > > -- > Jens Axboe > hi Jens, Sorry for not replying in time. We have basically determined the plan for the f2fs side. The short-term plan is to limit the size of a single bio, and the long-term plan is to change f2fs from page to folio to reduce the pagecache traversal time. However, I think it also makes sense to move less urgent work out of the IRQ top-half. Thanks Zhang
