diff options
Diffstat (limited to 'docs/all')
| -rw-r--r-- | docs/all/environment-setup.rst | 147 | ||||
| -rw-r--r-- | docs/all/index.rst | 44 | ||||
| -rw-r--r-- | docs/all/live_migration.rst | 108 | ||||
| -rw-r--r-- | docs/all/lmdowntime.jpg | bin | 0 -> 6372 bytes | |||
| -rw-r--r-- | docs/all/lmnetwork.jpg | bin | 0 -> 53332 bytes | |||
| -rw-r--r-- | docs/all/lmtotaltime.jpg | bin | 0 -> 24171 bytes | |||
| -rw-r--r-- | docs/all/tunning.rst | 97 |
7 files changed, 396 insertions, 0 deletions
diff --git a/docs/all/environment-setup.rst b/docs/all/environment-setup.rst new file mode 100644 index 000000000..b60deb7e0 --- /dev/null +++ b/docs/all/environment-setup.rst @@ -0,0 +1,147 @@ +Low Latency Environment +======================= + +Achieving low latency with the KVM4NFV project requires setting up a special +test environment. This environment includes the BIOS settings, kernel +configuration, kernel parameters and the run-time environment. + +Hardware Environment Description +-------------------------------- + +BIOS setup plays an important role in achieving real-time latency. A collection +of relevant settings, used on the platform where the baseline performance data +was collected, is detailed below: + +CPU Features +~~~~~~~~~~~~ + +Some special CPU features like TSC-deadline timer, invariant TSC and Process posted +interrupts, etc, are helpful for latency reduction. + +Below is the CPU information on the baseline test platform. +:: + processor : 35 + vendor_id : GenuineIntel + cpu family : 6 + model : 63 + model name : Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz + stepping : 2 + microcode : 0x2d + cpu MHz : 2294.795 + cache size : 46080 KB + physical id : 1 + siblings : 18 + core id : 27 + cpu cores : 18 + apicid : 118 + initial apicid : 118 + fpu : yes + fpu_exception : yes + cpuid level : 15 + wp : yes + flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge + mca cmov pat pse36 clflush dts acpi mmx fxsr sse + sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm + constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc + aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 + ssse3 fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt + tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm arat epb + pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase + tsc_adjust bmi1 avx2 smep bmi2 erms invpcid cqm xsaveopt cqm_llc + cqm_occup_llcbugs + bogomips : 4595.54 + clflush size : 64 + cache_alignment : 64 + address sizes : 46 bits physical, 48 bits virtual + power management: + +CPU Topology +~~~~~~~~~~~~ + +NUMA topology is also important for latency reduction. + +Below is the CPU topology on the baseline test platform. +:: + [nfv@otcnfv02 ~]$ lscpu + Architecture: x86_64 + CPU op-mode(s): 32-bit, 64-bit + Byte Order: Little Endian + CPU(s): 36 + On-line CPU(s) list: 0-35 + Thread(s) per core: 1 + Core(s) per socket: 18 + Socket(s): 2 + NUMA node(s): 2 + Vendor ID: GenuineIntel + CPU family: 6 + Model: 63 + Model name: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz + Stepping: 2 + CPU MHz: 2294.795 + BogoMIPS: 4595.54 + Virtualization: VT-x + L1d cache: 32K + L1i cache: 32K + L2 cache: 256K + L3 cache: 46080K + NUMA node0 CPU(s): 0-17 + NUMA node1 CPU(s): 18-35 + +BIOS Setup +~~~~~~~~~~ + +Careful BIOS setup is important in achieving real time latency. Different +platforms have different BIOS setups, below are the important BIOS settings on +the platform used to collect the baseline performance data. +:: + CPU Power and Performance <Performance> + CPU C-State <Disabled> + C1E Autopromote <Disabled> + Processor C3 <Disabled> + Processor C6 <Disabled> + Select Memory RAS <Maximum Performance> + NUMA Optimized <Enabled> + Cluster-on-Die <Disabled> + Patrol Scrub <Disabled> + Demand Scrub <Disabled> + Correctable Error <10> + Intel(R) Hyper-Threading <Disabled> + Active Processor Cores <All> + Execute Disable Bit <Enabled> + Intel(R) Virtualization Technology <Enabled> + Intel(R) TXT <Disabled> + Enhanced Error Containment Mode <Disabled> + USB Controller <Enabled> + USB 3.0 Controller <Auto> + Legacy USB Support <Disabled> + Port 60/64 Emulation <Disabled> + +Software Environment Setup +-------------------------- +Both the host and the guest environment need to be configured properly to +reduce latency variations. Below are some suggested kernel configurations. +The ci/envs/ directory gives detailed implementation on how to setup the +environment. + +Kernel Parameter +~~~~~~~~~~~~~~~~ + +Please check the default kernel configuration in the source code at: +kernel/arch/x86/configs/opnfv.config. + +Below is host kernel boot line example: +:: + isolcpus=11-15,31-35 nohz_full=11-15,31-35 rcu_nocbs=11-15,31-35 iommu=pt intel_iommu=on default_hugepagesz=1G hugepagesz=1G mce=off idle=poll intel_pstate=disable processor.max_cstate=1 pcie_asmp=off tsc=reliable + +Below is guest kernel boot line example +:: + isolcpus=1 nohz_full=1 rcu_nocbs=1 mce=off idle=poll default_hugepagesz=1G hugepagesz=1G + +Please refer to :doc:`tunning` for more explanation. + +Run-time Environment Setup +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Not only are special kernel parameters needed but a special run-time +environment is also required. Please refer to :doc:`tunning` for more +explanation. diff --git a/docs/all/index.rst b/docs/all/index.rst new file mode 100644 index 000000000..fb1b137d7 --- /dev/null +++ b/docs/all/index.rst @@ -0,0 +1,44 @@ +=============== +KVM4NFV project +=============== + +Welcome to KVM4NFV_ project! + + + +.. _KVM4NFV: https://wiki.opnfv.org/nfv-kvm + +Contents: + +KVM4NFV Project Description +=========================== + +The NFV hypervisors provide crucial functionality in the NFV Infrastructure +(NFVI). The existing hypervisors, however, are not necessarily designed or +targeted to meet the requirements for the NFVI, and we need to make +collaborative efforts toward enabling the NFV features. + +The KVM4NFV project focuses on the KVM hypervisor to enhance it for NFV, by +looking at the following areas + ++ Minimal Interrupt latency variation for data plane VNFs + * Minimal Timing Variation for Timing correctness of real-time VNFs + * Minimal packet latency variation for data-plane VNFs ++ Fast live migration + +While these items require software development and/or specific hardware features +there are also some adjustments that need to be made to system configuration +information, like hardware, BIOS, OS, etc. + +.. toctree:: + :numbered: + :maxdepth: 1 + +Setup Guides +============ +.. toctree:: + :maxdepth: 2 + + environment-setup + tunning + live_migration diff --git a/docs/all/live_migration.rst b/docs/all/live_migration.rst new file mode 100644 index 000000000..51265cc8d --- /dev/null +++ b/docs/all/live_migration.rst @@ -0,0 +1,108 @@ +Fast Live Migration +=================== + +The NFV project requires fast live migration. The specific requirement is total +live migration time < 2Sec, while keeping the VM down time < 10ms when running +DPDK L2 forwarding workload. + +We measured the baseline data of migrating an idle 8GiB guest running a DPDK L2 +forwarding work load and observed that the total live migration time was 2271ms +while the VM downtime was 26ms. Both of these two indicators failed to satisfy +the requirements. + +Current Challenges +------------------ + +The following 4 features have been developed over the years to make the live +migration process faster. + ++ XBZRLE: + Helps to reduce the network traffic by just sending the + compressed data. ++ RDMA: + Uses a specific NIC to increase the efficiency of data + transmission. ++ Multi thread compression: + Compresses the data before transmission. ++ Auto convergence: + Reduces the data rate of dirty pages. + +Tests show none of the above features can satisfy the requirement of NFV. +XBZRLE and Multi thread compression do the compression entirely in software and +they are not fast enough in a 10Gbps network environment. RDMA is not flexible +because it has to transport all the guest memory to the destination without zero +page optimization. Auto convergence is not appropriate for NFV because it will +impact guest’s performance. + +So we need to find other ways for optimization. + +Optimizations +------------------------- +a. Delay non-emergency operations + By profiling, it was discovered that some of the cleanup operations during + the stop and copy stage are the main reason for the long VM down time. The + cleanup operation includes stopping the dirty page logging, which is a time + consuming operation. By deferring these operations until the data transmission + is completed the VM down time is reduced to about 5-7ms. +b. Optimize zero page checking + Currently QEMU uses the SSE2 instruction to optimize the zero pages + checking. The SSE2 instruction can process 16 bytes per instruction. By using + the AVX2 instruction, we can process 32 bytes per instruction. Testingt shows + that using AVX2 can speed up the zero pages checking process by about 25%. +c. Remove unnecessary context synchronization. + The CPU context was being synchronized twice during live migration. Removing + this unnecessary synchronization shortened the VM downtime by about 100us. + +Test Environment +---------------- + +The source and destination host have the same hardware and OS: +:: +Host: HSW-EP +CPU: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz +RAM: 64G +OS: RHEL 7.1 +Kernel: 4.2 +QEMU v2.4.0 + +Ethernet controller: Intel Corporation Ethernet Controller 10-Gigabit X540-AT2 (rev 01) +QEMU parameters: +:: + /root/qemu.git/x86_64-softmmu/qemu-system-x86_64-enable-kvm -cpu host -smp 4 –device virtio-net-pci,netdev=net1,mac=52:54:00:12:34:56 –netdev type=tap,id=net1,script=/etc/kvm/qemu-ifup,downscript=no,vhost=on–device virtio-net-pci,netdev=net2,mac=54:54:00:12:34:56 –netdevtype=tap,id=net2,script=/etc/kvm/qemu-ifup2,downscript=no,vhost=on -balloon virtio -m 8192-monitor stdio /mnt/liang/ia32e_rhel6u5.qcow + +Network connection + +.. figure:: lmnetwork.jpg + :align: center + :alt: live migration network connection + :figwidth: 80% + + +Test Result +----------- +The down time is set to 10ms when doing the test. We use pktgen to send the +packages to guest, the package size is 64 bytes, and the line rate is 2013 +Mbps. + +a. Total live migration time + + The total live migration time before and after optimization is shown in the + chart below. For an idle guest, we can reduce the total live migration time + from 2070ms to 401ms. For a guest running the DPDK L2 forwarding workload, + the total live migration time is reduced from 2271ms to 654ms. + +.. figure:: lmtotaltime.jpg + :align: center + :alt: total live migration time + +b. VM downtime + + The VM down time before and after optimization is shown in the chart below. + For an idle guest, we can reduce the VM down time from 29ms to 9ms. For a guest + running the DPDK L2 forwarding workload, the VM down time is reduced from 26ms to + 5ms. + +.. figure:: lmdowntime.jpg + :align: center + :alt: vm downtime + :figwidth: 80% diff --git a/docs/all/lmdowntime.jpg b/docs/all/lmdowntime.jpg Binary files differnew file mode 100644 index 000000000..c9faa4c73 --- /dev/null +++ b/docs/all/lmdowntime.jpg diff --git a/docs/all/lmnetwork.jpg b/docs/all/lmnetwork.jpg Binary files differnew file mode 100644 index 000000000..8a9a324c3 --- /dev/null +++ b/docs/all/lmnetwork.jpg diff --git a/docs/all/lmtotaltime.jpg b/docs/all/lmtotaltime.jpg Binary files differnew file mode 100644 index 000000000..2dced3987 --- /dev/null +++ b/docs/all/lmtotaltime.jpg diff --git a/docs/all/tunning.rst b/docs/all/tunning.rst new file mode 100644 index 000000000..337255328 --- /dev/null +++ b/docs/all/tunning.rst @@ -0,0 +1,97 @@ +Low Latency Tunning Suggestion +============================== + +The correct configuration is critical for improving the NFV performance/latency. +Even working on the same codebase, configurations can cause wildly different +performance/latency results. + +There are many combinations of configurations, from hardware configuration to +Operating System configuration and application level configuration. And there +is no one simple configuration that works for every case. To tune a specific +scenario, it's important to know the behaviors of different configurations and +their impact. + +Platform Configuration +---------------------- + +Some hardware features can be configured through firmware interface(like BIOS) +but others may not be configurable (e.g. SMI on most platforms). + +* **Power management:** + Most power management related features save power at the + expensive of latency. These features include: Intel®Turbo Boost Technology, + Enhanced Intel®SpeedStep, Processor C state and P state. Normally they should + be disabled but, depending on the real-time application design and latency + requirements, there might be some features that can be enabled if the impact on + deterministic execution of the workload is small. + +* **Hyper-Threading:** + The logic cores that share resource with other logic cores can introduce + latency so the recommendation is to disable this feature for realtime use + cases. + +* **Legacy USB Support/Port 60/64 Emulation:** + These features involve some emulation in firmware and can introduce random + latency. It is recommended that they are disabled. + +* **SMI (System Management Interrupt):** + SMI runs outside of the kernel code and can potentially cause + latency. It is a pity there is no simple way to disable it. Some vendors may + provide related switches in BIOS but most machines do not have this capability. + +Operating System Configuration +------------------------------ + +* **CPU isolation:** + To achieve deterministic latency, dedicated CPUs should be allocated for + realtime application. This can be achieved by isolating cpus from kernel + scheduler. Please refer to + http://lxr.free-electrons.com/source/Documentation/kernel-parameters.txt#L1608 + for more information. + +* **Memory allocation:** + Memory shoud be reserved for realtime applications and usually hugepage should + be used to reduce page fauts/TLB misses. + +* **IRQ affinity:** + All the non-realtime IRQs should be affinitized to non realtime CPUs to + reduce the impact on realtime CPUs. Some OS distributions contain an irqbalance + daemon which balances the IRQs among all the cores dynamically. It should be + disabled as well. + +* **Device assignment for VM:** + If a device is used in a VM, then device passthrough is desirable. In this case, + the IOMMU should be enabled. + +* **Tickless:** + Frequent clock ticks cause latency. CONFIG_NOHZ_FULL should be enabled in the + linux kernel. With CONFIG_NOHZ_FULL, the physical CPU will trigger many fewer + clock tick interrupts(currently, 1 tick per second). This can reduce latency + because each host timer interrupt triggers a VM exit from guest to host which + causes performance/latency impacts. + +* **TSC:** + Mark TSC clock source as reliable. A TSC clock source that seems to be + unreliable causes the kernel to continuously enable the clock source watchdog + to check if TSC frequency is still correct. On recent Intel platforms with + Constant TSC/Invariant TSC/Synchronized TSC, the TSC is reliable so the + watchdog is useless but cause latency. + +* **Idle:** + The poll option forces a polling idle loop that can slightly improve the + performance of waking up an idle CPU. + +* **RCU_NOCB:** + RCU is a kernel synchronization mechanism. Refer to + http://lxr.free-electrons.com/source/Documentation/RCU/whatisRCU.txt for more + information. With RCU_NOCB, the impact from RCU to the VNF will be reduced. + +* **Disable the RT throttling:** + RT Throttling is a Linux kernel mechanism that + occurs when a process or thread uses 100% of the core, leaving no resources for + the Linux scheduler to execute the kernel/housekeeping tasks. RT Throttling + increases the latency so should be disabled. + +* **NUMA configuration:** + To achieve the best latency. CPU/Memory and device allocated for realtime + application/VM should be in the same NUMA node. |
