On 14/10/2018 01:09, Peng Hao wrote: > Coalesced pio is based on coalesced mmio and can be used for some port > like rtc port, pci-host config port and so on. > > Specially in case of rtc as coalesced pio, some versions of windows guest > access rtc frequently because of rtc as system tick. guest access rtc like > this: write register index to 0x70, then write or read data from 0x71. > writing 0x70 port is just as index and do nothing else. So we can use > coalesced pio to handle this scene to reduce VM-EXIT time. > > When starting and closing a virtual machine, it will access pci-host config > port frequently. So setting these port as coalesced pio can reduce startup > and shutdown time. > > without my patch, get the vm-exit time of accessing rtc 0x70 and piix 0xcf8 > using perf tools: (guest OS : windows 7 64bit) > IO Port Access Samples Samples% Time% Min Time Max Time Avg time > 0x70:POUT 86 30.99% 74.59% 9us 29us 10.75us (+- 3.41%) > 0xcf8:POUT 1119 2.60% 2.12% 2.79us 56.83us 3.41us (+- 2.23%) > > with my patch > IO Port Access Samples Samples% Time% Min Time Max Time Avg time > 0x70:POUT 106 32.02% 29.47% 0us 10us 1.57us (+- 7.38%) > 0xcf8:POUT 1065 1.67% 0.28% 0.41us 65.44us 0.66us (+- 10.55%) > > > Peng Hao (3): > kvm/x86 : add coalesced pio support > kvm/x86 : add document for coalesced mmio > kvm/x86 : add document for coalesced pio > > Documentation/virtual/kvm/api.txt | 28 +++++++++++++++++++++++++++ > include/uapi/linux/kvm.h | 11 +++++++++-- > virt/kvm/coalesced_mmio.c | 12 +++++++++--- > virt/kvm/kvm_main.c | 2 ++ > 4 files changed, 48 insertions(+), 5 deletions(-) > Queued, thanks (squashing 1 and 3 together). Paolo
