From: Paolo Bonzini <pbonzini@redhat.com>
To: root <yang.zhang.wz@gmail.com>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc: x86@kernel.org, corbet@lwn.net, tony.luck@intel.com,
bp@alien8.de, peterz@infradead.org, mchehab@kernel.org,
akpm@linux-foundation.org, krzk@kernel.org, jpoimboe@redhat.com,
luto@kernel.org, borntraeger@de.ibm.com, thgarnie@google.com,
rgerst@gmail.com, minipli@googlemail.com,
douly.fnst@cn.fujitsu.com, nicstange@gmail.com,
fweisbec@gmail.com, dvlasenk@redhat.com, bristot@redhat.com,
yamada.masahiro@socionext.com, mika.westerberg@linux.intel.com,
yu.c.chen@intel.com, aaron.lu@intel.com, rostedt@goodmis.org,
me@kylehuey.com, len.brown@intel.com, prarit@redhat.com,
hidehiro.kawai.ez@hitachi.com, fengtiantian@huawei.com,
pmladek@suse.com, jeyu@redhat.com, Larry.Finger@lwfinger.net,
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johannes.berg@intel.com, niklas.soderlund+renesas@ragnatech.se,
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mgorman@techsingularity.net, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-edac@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [PATCH 2/2] x86/idle: use dynamic halt poll
Date: Thu, 22 Jun 2017 13:51:14 +0200 [thread overview]
Message-ID: <4444ffc8-9e7b-5bd2-20da-af422fe834cc@redhat.com> (raw)
In-Reply-To: <1498130534-26568-3-git-send-email-root@ip-172-31-39-62.us-west-2.compute.internal>
On 22/06/2017 13:22, root wrote:
> ==============================================================
>
> +poll_grow: (X86 only)
> +
> +This parameter is multiplied in the grow_poll_ns() to increase the poll time.
> +By default, the values is 2.
> +
> +==============================================================
> +poll_shrink: (X86 only)
> +
> +This parameter is divided in the shrink_poll_ns() to reduce the poll time.
> +By default, the values is 2.
Even before starting the debate on whether this is a good idea or a bad
idea, KVM reduces the polling value to the minimum (10 us) by default
when polling fails. Also, it shouldn't be bound to
CONFIG_HYPERVISOR_GUEST, since there's nothing specific to virtual
machines here.
Regarding the good/bad idea part, KVM's polling is made much more
acceptable by single_task_running(). At least you need to integrate it
with paravirtualization. If the VM is scheduled out, you shrink the
polling period. There is already vcpu_is_preempted for this, it is used
by mutexes.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: root <yang.zhang.wz@gmail.com>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc: x86@kernel.org, corbet@lwn.net, tony.luck@intel.com,
bp@alien8.de, peterz@infradead.org, mchehab@kernel.org,
akpm@linux-foundation.org, krzk@kernel.org, jpoimboe@redhat.com,
luto@kernel.org, borntraeger@de.ibm.com, thgarnie@google.com,
rgerst@gmail.com, minipli@googlemail.com,
douly.fnst@cn.fujitsu.com, nicstange@gmail.com,
fweisbec@gmail.com, dvlasenk@redhat.com, bristot@redhat.com,
yamada.masahiro@socionext.com, mika.westerberg@linux.intel.com,
yu.c.chen@intel.com, aaron.lu@intel.com, rostedt@goodmis.org,
me@kylehuey.com, len.brown@intel.com, prarit@redhat.com,
hidehiro.kawai.ez@hitachi.com, fengtiantian@huawei.com,
pmladek@suse.com, jeyu@redhat.com, Larry.Finger@lwfinger.net,
zijun_hu@htc.com, luisbg@osg.samsung.com,
johannes.berg@intel.com, niklas.soderlund+renesas@ragnatech.se,
zlpnobody@gmail.com, adobriyan@gmail.com, fgao@ikuai8.com,
ebiederm@xmission.com, subashab@codeaurora.org, arnd@arndb.de,
matt@codeblueprint.co.uk, mgorman@techsingularity.net,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-edac@vger.kernel.org, kvm@vger.kernel.org
Subject: [2/2] x86/idle: use dynamic halt poll
Date: Thu, 22 Jun 2017 13:51:14 +0200 [thread overview]
Message-ID: <4444ffc8-9e7b-5bd2-20da-af422fe834cc@redhat.com> (raw)
On 22/06/2017 13:22, root wrote:
> ==============================================================
>
> +poll_grow: (X86 only)
> +
> +This parameter is multiplied in the grow_poll_ns() to increase the poll time.
> +By default, the values is 2.
> +
> +==============================================================
> +poll_shrink: (X86 only)
> +
> +This parameter is divided in the shrink_poll_ns() to reduce the poll time.
> +By default, the values is 2.
Even before starting the debate on whether this is a good idea or a bad
idea, KVM reduces the polling value to the minimum (10 us) by default
when polling fails. Also, it shouldn't be bound to
CONFIG_HYPERVISOR_GUEST, since there's nothing specific to virtual
machines here.
Regarding the good/bad idea part, KVM's polling is made much more
acceptable by single_task_running(). At least you need to integrate it
with paravirtualization. If the VM is scheduled out, you shrink the
polling period. There is already vcpu_is_preempted for this, it is used
by mutexes.
Paolo
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WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: root <yang.zhang.wz@gmail.com>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc: x86@kernel.org, corbet@lwn.net, tony.luck@intel.com,
bp@alien8.de, peterz@infradead.org, mchehab@kernel.org,
akpm@linux-foundation.org, krzk@kernel.org, jpoimboe@redhat.com,
luto@kernel.org, borntraeger@de.ibm.com, thgarnie@google.com,
rgerst@gmail.com, minipli@googlemail.com,
douly.fnst@cn.fujitsu.com, nicstange@gmail.com,
fweisbec@gmail.com, dvlasenk@redhat.com, bristot@redhat.com,
yamada.masahiro@socionext.com, mika.westerberg@linux.intel.com,
yu.c.chen@intel.com, aaron.lu@intel.com, rostedt@goodmis.org,
me@kylehuey.com, len.brown@intel.com, prarit@redhat.com,
hidehiro.kawai.ez@hitachi.com, fengtiantian@huawei.com,
pmladek@suse.com, jeyu@redhat.com, Larry.Finger@lwfinger.net,
zijun_hu@htc.com, luisbg@osg.samsung.com,
johannes.berg@intel.com, niklas.soderlund+renesas@ragnatech.se
Subject: Re: [PATCH 2/2] x86/idle: use dynamic halt poll
Date: Thu, 22 Jun 2017 13:51:14 +0200 [thread overview]
Message-ID: <4444ffc8-9e7b-5bd2-20da-af422fe834cc@redhat.com> (raw)
In-Reply-To: <1498130534-26568-3-git-send-email-root@ip-172-31-39-62.us-west-2.compute.internal>
On 22/06/2017 13:22, root wrote:
> ==============================================================
>
> +poll_grow: (X86 only)
> +
> +This parameter is multiplied in the grow_poll_ns() to increase the poll time.
> +By default, the values is 2.
> +
> +==============================================================
> +poll_shrink: (X86 only)
> +
> +This parameter is divided in the shrink_poll_ns() to reduce the poll time.
> +By default, the values is 2.
Even before starting the debate on whether this is a good idea or a bad
idea, KVM reduces the polling value to the minimum (10 us) by default
when polling fails. Also, it shouldn't be bound to
CONFIG_HYPERVISOR_GUEST, since there's nothing specific to virtual
machines here.
Regarding the good/bad idea part, KVM's polling is made much more
acceptable by single_task_running(). At least you need to integrate it
with paravirtualization. If the VM is scheduled out, you shrink the
polling period. There is already vcpu_is_preempted for this, it is used
by mutexes.
Paolo
next prev parent reply other threads:[~2017-06-22 11:52 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-22 11:22 [PATCH 0/2] x86/idle: add halt poll support root
2017-06-22 11:22 ` root
2017-06-22 11:22 ` [PATCH 1/2] x86/idle: add halt poll for halt idle root
2017-06-22 11:22 ` root
2017-06-22 11:22 ` [1/2] " Yang Zhang
2017-06-22 14:23 ` [PATCH 1/2] " Thomas Gleixner
2017-06-22 14:23 ` Thomas Gleixner
2017-06-22 14:23 ` [1/2] " Thomas Gleixner
2017-06-23 4:05 ` [PATCH 1/2] " Yang Zhang
2017-06-23 4:05 ` Yang Zhang
2017-06-23 4:05 ` [1/2] " Yang Zhang
2017-08-16 4:04 ` [PATCH 1/2] " Michael S. Tsirkin
2017-08-16 4:04 ` Michael S. Tsirkin
2017-08-16 4:04 ` [1/2] " Michael S. Tsirkin
2017-08-17 7:29 ` [PATCH 1/2] " Yang Zhang
2017-08-17 7:29 ` Yang Zhang
2017-08-17 7:29 ` [1/2] " Yang Zhang
2017-06-22 11:22 ` [PATCH 2/2] x86/idle: use dynamic halt poll root
2017-06-22 11:22 ` root
2017-06-22 11:22 ` [2/2] " Yang Zhang
2017-06-22 11:51 ` Paolo Bonzini [this message]
2017-06-22 11:51 ` [PATCH 2/2] " Paolo Bonzini
2017-06-22 11:51 ` [2/2] " Paolo Bonzini
2017-06-23 3:58 ` [PATCH 2/2] " Yang Zhang
2017-06-23 3:58 ` Yang Zhang
2017-06-23 3:58 ` [2/2] " Yang Zhang
2017-06-27 11:22 ` [PATCH 2/2] " Yang Zhang
2017-06-27 11:22 ` Yang Zhang
2017-06-27 11:22 ` [2/2] " Yang Zhang
2017-06-27 12:07 ` [PATCH 2/2] " Paolo Bonzini
2017-06-27 12:07 ` Paolo Bonzini
2017-06-27 12:07 ` [2/2] " Paolo Bonzini
2017-06-27 12:23 ` [PATCH 2/2] " Wanpeng Li
2017-06-27 12:23 ` Wanpeng Li
2017-06-27 12:23 ` [2/2] " Wanpeng Li
2017-06-27 12:28 ` [PATCH 2/2] " Paolo Bonzini
2017-06-27 12:28 ` Paolo Bonzini
2017-06-27 12:28 ` [2/2] " Paolo Bonzini
2017-06-27 13:40 ` [PATCH 2/2] " Radim Krčmář
2017-06-27 13:40 ` Radim Krčmář
2017-06-27 13:40 ` [2/2] " Radim Krčmář
2017-06-27 13:56 ` [PATCH 2/2] " Paolo Bonzini
2017-06-27 13:56 ` Paolo Bonzini
2017-06-27 13:56 ` [2/2] " Paolo Bonzini
2017-06-27 14:22 ` [PATCH 2/2] " Radim Krčmář
2017-06-27 14:22 ` Radim Krčmář
2017-06-27 14:22 ` [2/2] " Radim Krčmář
2017-06-27 14:26 ` [PATCH 2/2] " Paolo Bonzini
2017-06-27 14:26 ` Paolo Bonzini
2017-06-27 14:26 ` [2/2] " Paolo Bonzini
2017-07-03 9:28 ` [PATCH 2/2] " Yang Zhang
2017-07-03 9:28 ` Yang Zhang
2017-07-03 9:28 ` [2/2] " Yang Zhang
2017-07-03 10:06 ` [PATCH 2/2] " Thomas Gleixner
2017-07-03 10:06 ` Thomas Gleixner
2017-07-03 10:06 ` [2/2] " Thomas Gleixner
2017-07-04 2:19 ` [PATCH 2/2] " Yang Zhang
2017-07-04 2:19 ` Yang Zhang
2017-07-04 2:19 ` [2/2] " Yang Zhang
2017-07-04 14:13 ` [PATCH 2/2] " Radim Krčmář
2017-07-04 14:13 ` Radim Krčmář
2017-07-04 14:13 ` [2/2] " Radim Krčmář
2017-07-04 14:50 ` [PATCH 2/2] " Thomas Gleixner
2017-07-04 14:50 ` Thomas Gleixner
2017-07-04 14:50 ` [2/2] " Thomas Gleixner
2017-07-13 11:49 ` [PATCH 2/2] " Yang Zhang
2017-07-13 11:49 ` Yang Zhang
2017-07-13 11:49 ` [2/2] " Yang Zhang
2017-07-14 9:37 ` [PATCH 2/2] " Alexander Graf
2017-07-14 9:37 ` Alexander Graf
2017-07-14 9:37 ` [2/2] " Alexander Graf
2017-07-17 9:26 ` [PATCH 2/2] " Yang Zhang
2017-07-17 9:26 ` Yang Zhang
2017-07-17 9:26 ` [2/2] " Yang Zhang
2017-07-17 9:54 ` [PATCH 2/2] " Alexander Graf
2017-07-17 9:54 ` Alexander Graf
2017-07-17 9:54 ` [2/2] " Alexander Graf
2017-07-17 12:50 ` [PATCH 2/2] " Yang Zhang
2017-07-17 12:50 ` Yang Zhang
2017-07-17 12:50 ` [2/2] " Yang Zhang
2017-07-04 22:28 ` [PATCH 2/2] " Wanpeng Li
2017-07-04 22:28 ` Wanpeng Li
2017-07-04 22:28 ` [2/2] " Wanpeng Li
2017-06-22 14:32 ` [PATCH 2/2] " Thomas Gleixner
2017-06-22 14:32 ` Thomas Gleixner
2017-06-22 14:32 ` [2/2] " Thomas Gleixner
2017-06-23 4:04 ` [PATCH 2/2] " Yang Zhang
2017-06-23 4:04 ` Yang Zhang
2017-06-23 4:04 ` [2/2] " Yang Zhang
2017-06-22 22:46 ` [PATCH 2/2] " kbuild test robot
2017-06-22 22:46 ` kbuild test robot
2017-06-22 22:46 ` [2/2] " kbuild test robot
2017-06-22 11:32 ` [PATCH 0/2] x86/idle: add halt poll support Yang Zhang
2017-06-22 11:32 ` Yang Zhang
2017-06-22 11:50 ` Wanpeng Li
2017-06-22 11:50 ` Wanpeng Li
2017-06-23 4:08 ` Yang Zhang
2017-06-23 4:08 ` Yang Zhang
2017-06-23 4:35 ` Wanpeng Li
2017-06-23 4:35 ` Wanpeng Li
2017-06-23 6:49 ` Yang Zhang
2017-06-23 6:49 ` Yang Zhang
2017-06-27 14:00 ` Radim Krčmář
2017-06-27 14:00 ` Radim Krčmář
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