Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH 0/4] x86/hyper-v: optimize PV IPIs | Date | Wed, 27 Jun 2018 11:32:17 +0200 |
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Wanpeng Li <kernellwp@gmail.com> writes:
> Hi Vitaly, (fix my reply mess this time) > On Sat, 23 Jun 2018 at 01:09, Vitaly Kuznetsov <vkuznets@redhat.com> wrote: >> >> When reviewing my "x86/hyper-v: use cheaper HVCALL_FLUSH_VIRTUAL_ADDRESS_ >> {LIST,SPACE} hypercalls when possible" patch Michael suggested to apply the >> same idea to PV IPIs. Here we go! >> >> Despite what Hyper-V TLFS says about HVCALL_SEND_IPI hypercall, it can >> actually be 'fast' (passing parameters through registers). Use that too. >> >> This series can collide with my "KVM: x86: hyperv: PV IPI support for >> Windows guests" series as I rename ipi_arg_non_ex/ipi_arg_ex structures >> there. Depending on which one gets in first we may need to do tiny >> adjustments. > > As hyperv PV TLB flush has already been merged, is there any other > obvious multicast IPIs scenarios? qemu supports interrupt remapping > since two years ago, I think windows guest can switch to cluster mode > after entering x2APIC, so sending IPI per cluster. In addition, you > can also post the benchmark result for this PV IPI optimization, > although it also fixes the bug which you mentioned above.
I got confused, which of my patch series are you actually looking at? :-)
This particular one ("x86/hyper-v: optimize PV IPIs") is not about KVM/qemu, it is for Linux running on top on real Hyper-V server. We already support PV IPIs and here I'm just trying to optimize the way how we send them by switching to a cheaper hypercall (and using 'fast' version of it) when possible. I don't actually have a good benchmark (and I don't remember seeing one when K.Y. posted PV IPI support) but this can be arranged I guess: I can write a dump 'IPI sender' in kernel and send e.g. 1000 IPIs.
-- Vitaly
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