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([2001:b07:6468:f312:91e7:65e:d8cd:fdb3]) by smtp.gmail.com with ESMTPSA id r11sm114254839wre.14.2019.08.01.09.54.50 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 09:54:50 -0700 (PDT) Subject: Re: [PATCH] cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available To: "Rafael J. Wysocki" , Wanpeng Li , Marcelo Tosatti Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Linux PM References: <1564643196-7797-1-git-send-email-wanpengli@tencent.com> <7b1e3025-f513-7068-32ac-4830d67b65ac@intel.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: Date: Thu, 1 Aug 2019 18:54:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <7b1e3025-f513-7068-32ac-4830d67b65ac@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 01/08/19 18:51, Rafael J. Wysocki wrote: > On 8/1/2019 9:06 AM, Wanpeng Li wrote: >> From: Wanpeng Li >> >> The downside of guest side polling is that polling is performed even >> with other runnable tasks in the host. However, even if poll in kvm >> can aware whether or not other runnable tasks in the same pCPU, it >> can still incur extra overhead in over-subscribe scenario. Now we can >> just enable guest polling when dedicated pCPUs are available. >> >> Cc: Rafael J. Wysocki >> Cc: Paolo Bonzini >> Cc: Radim Krčmář >> Cc: Marcelo Tosatti >> Signed-off-by: Wanpeng Li > > Paolo, Marcelo, any comments? Yes, it's a good idea. Acked-by: Paolo Bonzini Paolo > >> --- >>   drivers/cpuidle/cpuidle-haltpoll.c   | 3 ++- >>   drivers/cpuidle/governors/haltpoll.c | 2 +- >>   2 files changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/cpuidle/cpuidle-haltpoll.c >> b/drivers/cpuidle/cpuidle-haltpoll.c >> index 9ac093d..7aee38a 100644 >> --- a/drivers/cpuidle/cpuidle-haltpoll.c >> +++ b/drivers/cpuidle/cpuidle-haltpoll.c >> @@ -53,7 +53,8 @@ static int __init haltpoll_init(void) >>         cpuidle_poll_state_init(drv); >>   -    if (!kvm_para_available()) >> +    if (!kvm_para_available() || >> +        !kvm_para_has_hint(KVM_HINTS_REALTIME)) >>           return 0; >>         ret = cpuidle_register(&haltpoll_driver, NULL); >> diff --git a/drivers/cpuidle/governors/haltpoll.c >> b/drivers/cpuidle/governors/haltpoll.c >> index 797477b..685c7007 100644 >> --- a/drivers/cpuidle/governors/haltpoll.c >> +++ b/drivers/cpuidle/governors/haltpoll.c >> @@ -141,7 +141,7 @@ static struct cpuidle_governor haltpoll_governor = { >>     static int __init init_haltpoll(void) >>   { >> -    if (kvm_para_available()) >> +    if (kvm_para_available() && kvm_para_has_hint(KVM_HINTS_REALTIME)) >>           return cpuidle_register_governor(&haltpoll_governor); >>         return 0; > >