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| author | Maciej S. Szmigiero <maciej.szmigiero@oracle.com> | 2021-02-08 19:51:32 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-02-09 14:42:09 +0100 |
| commit | 8f5c44f953d36f8c1aea6d57eb3251e3640f4dad (patch) | |
| tree | 39df906f8c5e159a51562d08d0a58c656e60b7ad /Documentation/virt | |
| parent | KVM: x86: hyper-v: Drop hv_vcpu_to_vcpu() helper (diff) | |
| download | linux-8f5c44f953d36f8c1aea6d57eb3251e3640f4dad.tar.xz linux-8f5c44f953d36f8c1aea6d57eb3251e3640f4dad.zip | |
KVM: x86/mmu: Make HVA handler retpoline-friendly
When retpolines are enabled they have high overhead in the inner loop
inside kvm_handle_hva_range() that iterates over the provided memory area.
Let's mark this function and its TDP MMU equivalent __always_inline so
compiler will be able to change the call to the actual handler function
inside each of them into a direct one.
This significantly improves performance on the unmap test on the existing
kernel memslot code (tested on a Xeon 8167M machine):
30 slots in use:
Test Before After Improvement
Unmap 0.0353s 0.0334s 5%
Unmap 2M 0.00104s 0.000407s 61%
509 slots in use:
Test Before After Improvement
Unmap 0.0742s 0.0740s None
Unmap 2M 0.00221s 0.00159s 28%
Looks like having an indirect call in these functions (and, so, a
retpoline) might have interfered with unrolling of the whole loop in the
CPU.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Message-Id: <732d3fe9eb68aa08402a638ab0309199fa89ae56.1612810129.git.maciej.szmigiero@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt')
0 files changed, 0 insertions, 0 deletions