[05/27] docs: virt: convert halt-polling.txt to ReST format

Message ID	b33f744ca5cdba1c0e3898c9c1aa50a2075b40f5.1580219586.git.mchehab+huawei@kernel.org (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=gQxY=3R=vger.kernel.org=kvm-owner@kernel.org> From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> To: Linux Media Mailing List <linux-media@vger.kernel.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>, Mauro Carvalho Chehab <mchehab@infradead.org>, Paolo Bonzini <pbonzini@redhat.com>, Jonathan Corbet <corbet@lwn.net>, kvm@vger.kernel.org, linux-doc@vger.kernel.org Subject: [PATCH 05/27] docs: virt: convert halt-polling.txt to ReST format Date: Tue, 28 Jan 2020 15:00:06 +0100 Message-Id: <b33f744ca5cdba1c0e3898c9c1aa50a2075b40f5.1580219586.git.mchehab+huawei@kernel.org> In-Reply-To: <cover.1580219586.git.mchehab+huawei@kernel.org> References: <cover.1580219586.git.mchehab+huawei@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: kvm-owner@vger.kernel.org Precedence: bulk
Series	docs: virt: convert text documents to ReST format \| expand [00/27] docs: virt: convert text documents to ReST format [12/27] docs: kvm: convert devices/vcpu.txt to ReST [01/27] docs: kvm: add arm/pvtime.rst to index.rst [05/27] docs: virt: convert halt-polling.txt to ReST format [06/27] docs: virt: Convert msr.txt to ReST format [07/27] docs: kvm: devices/arm-vgic-its.txt to ReST format [08/27] docs: kvm: devices/arm-vgit-v3.txt to ReST [09/27] docs: kvm: convert devices/arm-vgit.txt to ReST [10/27] docs: kvm: convert devices/mpic.txt to ReST [11/27] docs: kvm: convert devices/s390_flic.txt to ReST [13/27] docs: kvm: convert devices/vcpu.txt to ReST [14/27] docs: kvm: convert devices/vm.txt to ReST [15/27] docs: kvm: convert devices/xics.txt to ReST [16/27] docs: kvm: convert devices/xive.txt to ReST [18/27] docs: kvm: convert arm/hyp-abi.txt to ReST [19/27] docs: kvm: arm/psci.txt: convert to ReST [20/27] docs: kvm: Convert hypercalls.txt to ReST format [21/27] docs: kvm: Convert locking.txt to ReST format [22/27] docs: kvm: Convert mmu.txt to ReST format [23/27] docs: kvm: Convert nested-vmx.txt to ReST format [24/27] docs: kvm: Convert ppc-pv.txt to ReST format [25/27] docs: kvm: Convert s390-diag.txt to ReST format [26/27] docs: kvm: Convert timekeeping.txt to ReST format [27/27] docs: kvm: review-checklist.txt: rename to ReST

diff --git a/Documentation/virt/kvm/halt-polling.txt b/Documentation/virt/kvm/halt-polling.rst similarity index 64% rename from Documentation/virt/kvm/halt-polling.txt rename to Documentation/virt/kvm/halt-polling.rst index 4f791b128dd2..d8f7516bd8d9 100644 --- a/Documentation/virt/kvm/halt-polling.txt +++ b/Documentation/virt/kvm/halt-polling.rst @@ -1,3 +1,4 @@ +=========================== The KVM halt polling system =========================== @@ -68,7 +69,8 @@ steady state polling interval but will only really do a good job for wakeups which come at an approximately constant rate, otherwise there will be constant adjustment of the polling interval. -[0] total block time: the time between when the halt polling function is +[0] total block time: + the time between when the halt polling function is invoked and a wakeup source received (irrespective of whether the scheduler is invoked within that function). @@ -81,31 +83,32 @@ shrunk. These variables are defined in include/linux/kvm_host.h and as module parameters in virt/kvm/kvm_main.c, or arch/powerpc/kvm/book3s_hv.c in the powerpc kvm-hv case. -Module Parameter | Description | Default Value --------------------------------------------------------------------------------- -halt_poll_ns | The global max polling | KVM_HALT_POLL_NS_DEFAULT - | interval which defines | - | the ceiling value of the | - | polling interval for | (per arch value) - | each vcpu. | --------------------------------------------------------------------------------- -halt_poll_ns_grow | The value by which the | 2 - | halt polling interval is | - | multiplied in the | - | grow_halt_poll_ns() | - | function. | --------------------------------------------------------------------------------- -halt_poll_ns_grow_start | The initial value to grow | 10000 - | to from zero in the | - | grow_halt_poll_ns() | - | function. | --------------------------------------------------------------------------------- -halt_poll_ns_shrink | The value by which the | 0 - | halt polling interval is | - | divided in the | - | shrink_halt_poll_ns() | - | function. | --------------------------------------------------------------------------------- ++-----------------------+---------------------------+-------------------------+ +|Module Parameter | Description | Default Value | ++-----------------------+---------------------------+-------------------------+ +|halt_poll_ns | The global max polling | KVM_HALT_POLL_NS_DEFAULT| +| | interval which defines | | +| | the ceiling value of the | | +| | polling interval for | (per arch value) | +| | each vcpu. | | ++-----------------------+---------------------------+-------------------------+ +|halt_poll_ns_grow | The value by which the | 2 | +| | halt polling interval is | | +| | multiplied in the | | +| | grow_halt_poll_ns() | | +| | function. | | ++-----------------------+---------------------------+-------------------------+ +|halt_poll_ns_grow_start| The initial value to grow | 10000 | +| | to from zero in the | | +| | grow_halt_poll_ns() | | +| | function. | | ++-----------------------+---------------------------+-------------------------+ +|halt_poll_ns_shrink | The value by which the | 0 | +| | halt polling interval is | | +| | divided in the | | +| | shrink_halt_poll_ns() | | +| | function. | | ++-----------------------+---------------------------+-------------------------+ These module parameters can be set from the debugfs files in: @@ -117,20 +120,19 @@ Note: that these module parameters are system wide values and are not able to Further Notes ============= -- Care should be taken when setting the halt_poll_ns module parameter as a -large value has the potential to drive the cpu usage to 100% on a machine which -would be almost entirely idle otherwise. This is because even if a guest has -wakeups during which very little work is done and which are quite far apart, if -the period is shorter than the global max polling interval (halt_poll_ns) then -the host will always poll for the entire block time and thus cpu utilisation -will go to 100%. +- Care should be taken when setting the halt_poll_ns module parameter as a large value + has the potential to drive the cpu usage to 100% on a machine which would be almost + entirely idle otherwise. This is because even if a guest has wakeups during which very + little work is done and which are quite far apart, if the period is shorter than the + global max polling interval (halt_poll_ns) then the host will always poll for the + entire block time and thus cpu utilisation will go to 100%. -- Halt polling essentially presents a trade off between power usage and latency -and the module parameters should be used to tune the affinity for this. Idle -cpu time is essentially converted to host kernel time with the aim of decreasing -latency when entering the guest. +- Halt polling essentially presents a trade off between power usage and latency and + the module parameters should be used to tune the affinity for this. Idle cpu time is + essentially converted to host kernel time with the aim of decreasing latency when + entering the guest. -- Halt polling will only be conducted by the host when no other tasks are -runnable on that cpu, otherwise the polling will cease immediately and -schedule will be invoked to allow that other task to run. Thus this doesn't -allow a guest to denial of service the cpu. +- Halt polling will only be conducted by the host when no other tasks are runnable on + that cpu, otherwise the polling will cease immediately and schedule will be invoked to + allow that other task to run. Thus this doesn't allow a guest to denial of service the + cpu. diff --git a/Documentation/virt/kvm/index.rst b/Documentation/virt/kvm/index.rst index 488c6370a447..b39f4894b61d 100644 --- a/Documentation/virt/kvm/index.rst +++ b/Documentation/virt/kvm/index.rst @@ -9,6 +9,7 @@ KVM amd-memory-encryption cpuid + halt-polling vcpu-requests arm/index

[05/27] docs: virt: convert halt-polling.txt to ReST format

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