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89d9a43c1d
Thread creation requires taking the mmap_sem in write mode, which causes vCPU threads running in guest mode to block while they are populating memory. Fix this by waiting for all vCPU threads to be created and start running before entering guest mode on any one vCPU thread. This substantially improves the "Populate memory time" when using 1GiB pages since it allows all vCPUs to zero pages in parallel rather than blocking because a writer is waiting (which is waiting for another vCPU that is busy zeroing a 1GiB page). Before: $ ./dirty_log_perf_test -v256 -s anonymous_hugetlb_1gb ... Populate memory time: 52.811184013s After: $ ./dirty_log_perf_test -v256 -s anonymous_hugetlb_1gb ... Populate memory time: 10.204573342s Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20211111001257.1446428-4-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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