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Date: Mon, 31 Aug 2015 15:44:32 +0800 From: Wanpeng Li <wanpeng.li@...mail.com> To: Peter Kieser <peter@...ser.ca> CC: Paolo Bonzini <pbonzini@...hat.com>, David Matlack <dmatlack@...gle.com>, kvm <kvm@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v4 0/3] KVM: Dynamic Halt-Polling On 8/30/15 6:26 AM, Peter Kieser wrote: > 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: Interesting. I test this against latest kvm tree and stable qemu 2.0.0, 4 vCPUs on pCPU0(other pCPUs are offline to easy observe %C0 and to avoid vCPUs schedule overhead influence). I just ignore the fluctuation and post the most common result of %C0 against the Windows 10 x86 guest. +-----------------+----------------+-----------------------+ | | | | | w/o halt-poll | w/ halt-poll | dynamic(v4) halt-poll | +-----------------+----------------+-----------------------+ | | | | | ~2.1% | ~3.0% | ~2.4% | +-----------------+----------------+-----------------------+ Regards, Wanpeng Li > > 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(-) >>> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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