KVM: try __get_user_pages_fast even if not in atomic context
We are currently cutting hva_to_pfn_fast short if we do not want an immediate exit, which is represented by !async && !atomic. However, this is unnecessary, and __get_user_pages_fast is *much* faster because the regular get_user_pages takes pmd_lock/pte_lock. In fact, when many CPUs take a nested vmexit at the same time the contention on those locks is visible, and this patch removes about 25% (compared to 4.18) from vmexit.flat on a 16 vCPU nested guest. Suggested-by: NAndrea Arcangeli <aarcange@redhat.com> Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Showing
想要评论请 注册 或 登录