> On Jun 18, 2024, at 2:32 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > I recently back ported Neil's lwq code and sunrpc server changes to our > 5.15.130 based kernel in the hope of improving the performance for our > data servers. > > Our performance team recently ran a fio workload on a client that was > doing 100% NFSv3 reads in O_DIRECT mode over an RDMA connection > (infiniband) against that resulting server. I've attached the resulting > flame graph from a perf profile run on the server side. > > Is anyone else seeing this massive contention for the spin lock in > __lwq_dequeue? As you can see, it appears to be dwarfing all the other > nfsd activity on the system in question here, being responsible for 45% > of all the perf hits. I haven't seen that, but I've been working on other issues. What's the nfsd thread count on your test server? Have you seen a similar impact on 6.10 kernels ? -- Chuck Lever
