Messages in this thread | | | From | Konrad Rzeszutek Wilk <> | Subject | [RFC PATCH] Use vAPIC when doing IPI for PVHVM guests. | Date | Wed, 7 Oct 2015 16:21:48 -0400 |
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Hey,
I was running some tools in which we would heavily do rescheduling of events - and realized to my surprise that the event channels (and the hypercall) would slow things down. If I used the vAPIC with its IPI support (so no VMEXIT) I got much much better performance.
Now this is an RFC because: 1). I hadn't verified from the xentrace how much less VMEXITS we get. But I remember Boris's patches and they gave at least 10%. I think this will get the same performance or even better.
2). I don't know what to do with migration. That is if the guest migrates to older hardware it needs to recheck this I presume?
3). Should this be enabled by default? I did get better performance but that was synthetic.
Thoughts?
Documentation/kernel-parameters.txt | 15 +++++------ arch/x86/xen/enlighten.c | 50 +++++++++++++++++++++++++++++++++---- arch/x86/xen/smp.c | 22 ++++++++++++++-- arch/x86/xen/spinlock.c | 18 ++++--------- arch/x86/xen/xen-ops.h | 4 +++ 5 files changed, 82 insertions(+), 27 deletions(-)
Konrad Rzeszutek Wilk (2): xen/apic: Use vAPIC for IPI if the hardware supports it. xen_nopv: Combine a bunch of the PV features that can be disabled
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