Public bug reported: [Impact] The current design of hisi_sas_task_prep() has two critical sections protected by different spin locks. This can lead to unnecessary thrashing. By merging the critical sections under one spin lock, we can avoid this.
[Test Case] Use fio to measure performance difference, and verify that there is no performance decrease. Sample config attached. Test on D05 and D06 systems, since both are impacted. [Fix] commit 6cca51ee0aa2540d648ff8698c3889330d897f27 Author: Xiang Chen <[email protected]> Date: Wed Jul 18 22:14:31 2018 +0800 scsi: hisi_sas: Tidy hisi_sas_task_prep() [Regression Risk] It's possible that decreasing the lock granularity like this will lead to unforeseen latency issues. However, the additional work done under the new spin lock is just a single list_add_tail() call, which appears to run in constant time. ** Affects: linux (Ubuntu) Importance: Undecided Assignee: dann frazier (dannf) Status: In Progress ** Affects: linux (Ubuntu Bionic) Importance: Undecided Assignee: dann frazier (dannf) Status: In Progress ** Attachment added: "fio" https://bugs.launchpad.net/bugs/1794165/+attachment/5192579/+files/fio ** Also affects: linux (Ubuntu Bionic) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Bionic) Status: New => In Progress ** Changed in: linux (Ubuntu Bionic) Assignee: (unassigned) => dann frazier (dannf) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1794165 Title: hisi_sas: Reduce unnecessary spin lock contention To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1794165/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
