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* [Qemu-devel] [PATCH v6 0/2] kvm: limited x86 CPU power management
@ 2018-06-22 19:22 Michael S. Tsirkin
  2018-06-22 19:22 ` [Qemu-devel] [PATCH v6 1/2] kvm: support -overcommit cpu-pm=on|off Michael S. Tsirkin
                   ` (5 more replies)
  0 siblings, 6 replies; 13+ messages in thread
From: Michael S. Tsirkin @ 2018-06-22 19:22 UTC (permalink / raw)
  To: qemu-devel
  Cc: Paolo Bonzini, Richard Henderson, Eduardo Habkost,
	Marcelo Tosatti, kvm

This adds ability to expose some host CPU power management capabilities
to guests. For intel guests, this is sufficient for guest to enable low
power CPU states on idle. For AMD guests it isn't sufficient, deeper
C-states are entered using System-IO.

When enabled this puts CPU in a low power state with exit latencies that
can go up to multiple milliseconds, and makes host scheduler as well as
host utilities such as top and powertop think the CPU is constantly
busy.  Thus it has the effect of dedicating a host CPU for this guest.

mwait based power management is tied closely to specifics of CPUID,
making migration challenging. At this point only the non-migrateable
-cpu host is supported.

With this patch applied, VM latency is within the noise of
baremetal for some benchmarks.

perf bench sched pipe results:
Before:
    6.452 sec
After:
    4.382 sec
Baremetal:
    4.136 sec

Changes since v5:
    Typo fix.

Changes since v4:
    See v3, now for real.

Changes since v3:
    At Paolo's suggestion, rename -dedicated to -overcommit.

Changes since v2:
    At Daniel's suggestion, don't use the -realtime flag.

    At Paolo's suggestion, group this with memory lock flag
    which has a similar effect of dedicating memory to this VM.

Michael S. Tsirkin (2):
  kvm: support -overcommit cpu-pm=on|off
  i386/cpu: make -cpu host support monitor/mwait

 include/sysemu/sysemu.h |  1 +
 target/i386/cpu.h       |  9 +++++++++
 target/i386/cpu.c       | 19 ++++++++++++++-----
 target/i386/kvm.c       | 32 ++++++++++++++++++++++++++++++++
 vl.c                    | 32 +++++++++++++++++++++++++++++++-
 qemu-options.hx         | 27 +++++++++++++++++++++++++--
 6 files changed, 112 insertions(+), 8 deletions(-)

-- 
MST

^ permalink raw reply	[flat|nested] 13+ messages in thread

end of thread, other threads:[~2018-06-27 15:08 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-06-22 19:22 [Qemu-devel] [PATCH v6 0/2] kvm: limited x86 CPU power management Michael S. Tsirkin
2018-06-22 19:22 ` [Qemu-devel] [PATCH v6 1/2] kvm: support -overcommit cpu-pm=on|off Michael S. Tsirkin
2018-06-25  9:40   ` Igor Mammedov
2018-06-26 14:06     ` Michael S. Tsirkin
2018-06-26 15:13       ` Igor Mammedov
2018-06-26 15:16         ` Michael S. Tsirkin
2018-06-27 13:42           ` Eduardo Habkost
2018-06-27 13:43   ` Eduardo Habkost
2018-06-22 19:22 ` [Qemu-devel] [PATCH v6 2/2] i386/cpu: make -cpu host support monitor/mwait Michael S. Tsirkin
2018-06-22 21:55 ` [Qemu-devel] [PATCH v6 0/2] kvm: limited x86 CPU power management no-reply
2018-06-22 22:03 ` no-reply
2018-06-22 22:16 ` no-reply
2018-06-27 15:08 ` Paolo Bonzini

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