On Tue, Oct 27, 2020 at 04:37:33PM -0700, Ben Gardon wrote: > The dirty log perf test will time verious dirty logging operations > (enabling dirty logging, dirtying memory, getting the dirty log, > clearing the dirty log, and disabling dirty logging) in order to > quantify dirty logging performance. This test can be used to inform > future performance improvements to KVM's dirty logging infrastructure. One thing to mention is that there're a few patches in the kvm dirty ring series that reworked the dirty log test quite a bit (to add similar test for dirty ring). For example: https://lore.kernel.org/kvm/20201023183358.50607-11-peterx@xxxxxxxxxx/ Just a FYI if we're going to use separate test programs. Merging this tests should benefit in many ways, of course (e.g., dirty ring may directly runnable with the perf tests too; so we can manually enable this "perf mode" as a new parameter in dirty_log_test, if possible?), however I don't know how hard - maybe there's some good reason to keep them separate... [...] > +static void run_test(enum vm_guest_mode mode, unsigned long iterations, > + uint64_t phys_offset, int vcpus, > + uint64_t vcpu_memory_bytes, int wr_fract) > +{ [...] > + /* Start the iterations */ > + iteration = 0; > + host_quit = false; > + > + clock_gettime(CLOCK_MONOTONIC, &start); > + for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) { > + pthread_create(&vcpu_threads[vcpu_id], NULL, vcpu_worker, > + &perf_test_args.vcpu_args[vcpu_id]); > + } > + > + /* Allow the vCPU to populate memory */ > + pr_debug("Starting iteration %lu - Populating\n", iteration); > + while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration) > + pr_debug("Waiting for vcpu_last_completed_iteration == %lu\n", > + iteration); Isn't array vcpu_last_completed_iteration[] initialized to all zeros? If so, I feel like this "while" won't run as expected to wait for populating mem. The flooding pr_debug() seems a bit scary too if the mem size is huge.. How about a pr_debug() after the loop (so if we don't see that it means it hanged)? (There's another similar pr_debug() after this point too within a loop) Thanks, -- Peter Xu
