Messages in this thread Patch in this message | | | From | Avi Kivity <> | Subject | [PATCH 07/20] KVM: Avoid useless memory write when possible | Date | Sun, 8 Jul 2007 14:54:36 +0300 |
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From: Luca Tettamanti <kronos.it@gmail.com>
When writing to normal memory and the memory area is unchanged the write can be safely skipped, avoiding the costly kvm_mmu_pte_write.
Signed-Off-By: Luca Tettamanti <kronos.it@gmail.com> Signed-off-by: Avi Kivity <avi@qumranet.com> --- drivers/kvm/kvm_main.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c index 7826f16..5603000 100644 --- a/drivers/kvm/kvm_main.c +++ b/drivers/kvm/kvm_main.c @@ -1170,8 +1170,10 @@ static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa, return 0; mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT); virt = kmap_atomic(page, KM_USER0); - kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes); - memcpy(virt + offset_in_page(gpa), val, bytes); + if (memcmp(virt + offset_in_page(gpa), val, bytes)) { + kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes); + memcpy(virt + offset_in_page(gpa), val, bytes); + } kunmap_atomic(virt, KM_USER0); return 1; } -- 1.5.2.2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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