Re: [RFC PATCH] KVM: x86: Skip request checking branches in vcpu_enter_guest() more effectively

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

On 09/24/2012 02:24 PM, Takuya Yoshikawa wrote:
> This is an RFC since I have not done any comparison with the approach
> using for_each_set_bit() which can be seen in Avi's work.
> 

Why not compare it? I think for_each_set_bit is better and it can
improve for all cases (in your patch, you did not consider all case,
for example, if the guest under mm overcommit, it should generate
lots of TLB flush/RELOAD request).

Actually, i think Avi's way can be improved in the further, we can
just use one atomic operation to avoid cache-miss. May be like this:

while (vcpu->request) {
	xchg(vcpu->request, request);

	for_each_set_bit(request) {
		clear_bit(X);

		......
	}
	
}