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This test measures the performance effects of KVM's access tracking. Access tracking is driven by the MMU notifiers test_young, clear_young, and clear_flush_young. These notifiers do not have a direct userspace API, however the clear_young notifier can be triggered by marking a pages as idle in /sys/kernel/mm/page_idle/bitmap. This test leverages that mechanism to enable access tracking on guest memory. To measure performance this test runs a VM with a configurable number of vCPUs that each touch every page in disjoint regions of memory. Performance is measured in the time it takes all vCPUs to finish touching their predefined region. Example invocation: $ ./access_tracking_perf_test -v 8 Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages guest physical test memory offset: 0xffdfffff000 Populating memory : 1.337752570s Writing to populated memory : 0.010177640s Reading from populated memory : 0.009548239s Mark memory idle : 23.973131748s Writing to idle memory : 0.063584496s Mark memory idle : 24.924652964s Reading from idle memory : 0.062042814s Breaking down the results: * "Populating memory": The time it takes for all vCPUs to perform the first write to every page in their region. * "Writing to populated memory" / "Reading from populated memory": The time it takes for all vCPUs to write and read to every page in their region after it has been populated. This serves as a control for the later results. * "Mark memory idle": The time it takes for every vCPU to mark every page in their region as idle through page_idle. * "Writing to idle memory" / "Reading from idle memory": The time it takes for all vCPUs to write and read to every page in their region after it has been marked idle. This test should be portable across architectures but it is only enabled for x86_64 since that's all I have tested. Reviewed-by: Ben Gardon <bgardon@google.com> Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210713220957.3493520-7-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| .. | ||
| aarch64 | ||
| include | ||
| lib | ||
| s390x | ||
| x86_64 | ||
| .gitignore | ||
| access_tracking_perf_test.c | ||
| config | ||
| demand_paging_test.c | ||
| dirty_log_perf_test.c | ||
| dirty_log_test.c | ||
| hardware_disable_test.c | ||
| kvm_binary_stats_test.c | ||
| kvm_create_max_vcpus.c | ||
| kvm_page_table_test.c | ||
| Makefile | ||
| memslot_modification_stress_test.c | ||
| memslot_perf_test.c | ||
| set_memory_region_test.c | ||
| settings | ||
| steal_time.c | ||