From: Marcelo Tosatti <mtosatti@redhat.com>
To: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
joao.m.martins@oracle.com, rafael.j.wysocki@intel.com,
rkrcmar@redhat.com, pbonzini@redhat.com
Subject: Re: [PATCH 1/5] KVM: simplify branch check in host poll code
Date: Fri, 1 Nov 2019 19:03:32 -0200 [thread overview]
Message-ID: <20191101210331.GA20061@amt.cnet> (raw)
In-Reply-To: <1572060239-17401-2-git-send-email-zhenzhong.duan@oracle.com>
On Sat, Oct 26, 2019 at 11:23:55AM +0800, Zhenzhong Duan wrote:
> Remove redundant check.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> ---
> virt/kvm/kvm_main.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 67ef3f2..2ca2979 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2366,13 +2366,12 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> } else if (halt_poll_ns) {
> if (block_ns <= vcpu->halt_poll_ns)
> ;
> - /* we had a long block, shrink polling */
> - else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
> - shrink_halt_poll_ns(vcpu);
> /* we had a short halt and our poll time is too small */
> - else if (vcpu->halt_poll_ns < halt_poll_ns &&
This is not a redundant check: it avoids from calling
into grow_halt_poll_ns, which will do:
1) Multiplication
2) Cap that back to halt_poll_ns
3) Invoke the trace_kvm_halt_poll_ns_grow tracepoint
(when in fact vcpu->halt_poll_ns did not grow).
next prev parent reply other threads:[~2019-11-01 21:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-26 3:23 [PATCH 0/5] misc fixes on halt-poll code both KVM and guest Zhenzhong Duan
2019-10-26 3:23 ` [PATCH 1/5] KVM: simplify branch check in host poll code Zhenzhong Duan
2019-11-01 21:03 ` Marcelo Tosatti [this message]
2019-11-04 3:49 ` Zhenzhong Duan
2019-10-26 3:23 ` [PATCH 2/5] KVM: add a check to ensure grow start value is nonzero Zhenzhong Duan
2019-11-11 13:49 ` Paolo Bonzini
2019-10-26 3:23 ` [PATCH 3/5] KVM: ensure pool time is longer than block_ns Zhenzhong Duan
2019-11-01 21:16 ` Marcelo Tosatti
2019-11-11 13:53 ` Paolo Bonzini
2019-11-12 12:14 ` Zhenzhong Duan
2019-10-26 3:23 ` [PATCH 4/5] cpuidle-haltpoll: add a check to ensure grow start value is nonzero Zhenzhong Duan
2019-11-01 21:19 ` Marcelo Tosatti
2019-11-04 2:56 ` Zhenzhong Duan
2019-11-11 13:54 ` Paolo Bonzini
2019-10-26 3:23 ` [PATCH 5/5] cpuidle-haltpoll: fix up the branch check Zhenzhong Duan
2019-11-01 21:26 ` Marcelo Tosatti
2019-11-04 3:10 ` Zhenzhong Duan
2019-11-04 15:01 ` Marcelo Tosatti
2019-11-05 6:49 ` Zhenzhong Duan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191101210331.GA20061@amt.cnet \
--to=mtosatti@redhat.com \
--cc=joao.m.martins@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=rafael.j.wysocki@intel.com \
--cc=rkrcmar@redhat.com \
--cc=zhenzhong.duan@oracle.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).