On Tue, Aug 27, 2024 at 8:35 AM Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx> wrote: > > The wait_for_overlap wait queue is currently used in two cases, which > are not really related: > - waiting for actual overlapping bios, which uses R5_Overlap bit, > - waiting for events related to reshape. > > Handling every write request in raid5_make_request() involves adding to > and removing from this wait queue, which uses a spinlock. With fast > storage and multiple submitting threads the contention on this lock is > noticeable. > > This patch series aims to resolve this by separating the two cases > mentioned above and using this wait queue only when reshape is in > progress. > > The results when testing 4k random writes on raid5 with null_blk > (8 jobs, qd=64, group_thread_cnt=8): > before: 463k IOPS > after: 523k IOPS > > The improvement is not huge with this series alone but it is just one of > the bottlenecks. When applied onto some other changes I'm working on, it > allowed to go from 845k IOPS to 975k IOPS on the same test. > > Artur Paszkiewicz (3): > md/raid5: use wait_on_bit() for R5_Overlap > md/raid5: only add to wait queue if reshape is in progress > md/raid5: rename wait_for_overlap to wait_for_reshape Thanks for the optimization! Applied the set to md-6.12 branch. Song
