Messages in this thread | | | Subject | Re: [PATCH v4 0/3] KVM: Dynamic Halt-Polling | From | Peter Kieser <> | Date | Sat, 29 Aug 2015 15:26:11 -0700 |
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Thanks, Wanpeng. Applied this to Linux 3.18 and seeing much higher CPU usage (200%) for qemu 2.4.0 process on a Windows 10 x64 guest. qemu parameters:
qemu-system-x86_64 -enable-kvm -name arwan-20150704 -S -machine pc-q35-2.2,accel=kvm,usb=off -cpu Haswell,hv_time,hv_relaxed,hv_vapic,hv_spinlocks=0x1000 -m 8192 -realtime mlock=off -smp 4,sockets=4,cores=1,threads=1 -uuid 7c2fc02d-2798-4fc9-ad04-db5f1af92723 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/arwan-20150704.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -no-shutdown -boot strict=on -device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1e -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1 -device nec-usb-xhci,id=usb1,bus=pci.2,addr=0x4 -device virtio-serial-pci,id=virtio-serial0,bus=pci.2,addr=0x5 -drive file=/dev/mapper/crypt-arwan-20150704,if=none,id=drive-virtio-disk0,format=raw,cache=none,discard=unmap,aio=native -device virtio-blk-pci,scsi=off,bus=pci.2,addr=0x3,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=2 -drive file=/usr/share/virtio-win/virtio-win.iso,if=none,media=cdrom,id=drive-sata0-0-2,readonly=on,format=raw -device ide-cd,bus=ide.2,drive=drive-sata0-0-2,id=sata0-0-2,bootindex=1 -netdev tap,fds=31:32:33:34,id=hostnet0,vhost=on,vhostfds=35:36:37:38 -device virtio-net-pci,guest_csum=off,guest_tso4=off,guest_tso6=off,mq=on,vectors=10,netdev=hostnet0,id=net0,mac=52:54:00:f3:6b:c4,bus=pci.2,addr=0x2 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/channel/target/arwan-20150704.org.qemu.guest_agent.0,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -chardev spicevmc,id=charchannel1,name=vdagent -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=com.redhat.spice.0 -vnc 127.0.0.1:4 -device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vgamem_mb=16,bus=pcie.0,addr=0x1 -device virtio-balloon-pci,id=balloon0,bus=pci.2,addr=0x1 -msg timestamp=on
I revert patch, qemu shows 17% CPU usage on host. Thoughts?
-Peter
On 2015-08-29 3:21 PM, Wanpeng Li wrote: > Hi Peter, > On 8/30/15 5:18 AM, Peter Kieser wrote: >> Hi Wanpeng, >> >> Do I need to set any module parameters to use your patch, or should >> halt_poll_ns automatically tune with just your patch series applied? >> > > You don't need any module parameters. > > Regards, > Wanpeng Li > >> Thanks. >> >> On 2015-08-27 2:47 AM, Wanpeng Li wrote: >>> v3 -> v4: >>> * bring back grow vcpu->halt_poll_ns when interrupt arrives and >>> shrinks >>> when idle VCPU is detected >>> >>> v2 -> v3: >>> * grow/shrink vcpu->halt_poll_ns by *halt_poll_ns_grow or >>> /halt_poll_ns_shrink >>> * drop the macros and hard coding the numbers in the param >>> definitions >>> * update the comments "5-7 us" >>> * remove halt_poll_ns_max and use halt_poll_ns as the max >>> halt_poll_ns time, >>> vcpu->halt_poll_ns start at zero >>> * drop the wrappers >>> * move the grow/shrink logic before "out:" w/ "if (waited)" >>> >>> v1 -> v2: >>> * change kvm_vcpu_block to read halt_poll_ns from the vcpu instead of >>> the module parameter >>> * use the shrink/grow matrix which is suggested by David >>> * set halt_poll_ns_max to 2ms >>> >>> There is a downside of halt_poll_ns since poll is still happen for idle >>> VCPU which can waste cpu usage. This patchset add the ability to adjust >>> halt_poll_ns dynamically, grows halt_poll_ns if an interrupt arrives >>> and >>> shrinks halt_poll_ns when idle VCPU is detected. >>> >>> There are two new kernel parameters for changing the halt_poll_ns: >>> halt_poll_ns_grow and halt_poll_ns_shrink. >>> >>> >>> Test w/ high cpu overcommit ratio, pin vCPUs, and the halt_poll_ns of >>> halt-poll is the default 500000ns, the max halt_poll_ns of dynamic >>> halt-poll is 2ms. Then watch the %C0 in the dump of Powertop tool. >>> The test method is almost from David. >>> >>> +-----------------+----------------+-------------------+ >>> | | | | >>> | w/o halt-poll | w/ halt-poll | dynamic halt-poll | >>> +-----------------+----------------+-------------------+ >>> | | | | >>> | ~0.9% | ~1.8% | ~1.2% | >>> +-----------------+----------------+-------------------+ >>> The always halt-poll >>> will increase ~0.9% cpu usage for idle vCPUs and the >>> dynamic halt-poll drop it to ~0.3% which means that reduce the 67% >>> overhead >>> introduced by always halt-poll. >>> >>> Wanpeng Li (3): >>> KVM: make halt_poll_ns per-VCPU >>> KVM: dynamic halt_poll_ns adjustment >>> KVM: trace kvm_halt_poll_ns grow/shrink >>> >>> include/linux/kvm_host.h | 1 + >>> include/trace/events/kvm.h | 30 ++++++++++++++++++++++++++++ >>> virt/kvm/kvm_main.c | 50 >>> +++++++++++++++++++++++++++++++++++++++++++--- >>> 3 files changed, 78 insertions(+), 3 deletions(-) >> >
-- Peter Kieser 604.338.9294 / peter@kieser.ca
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