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Re: [Xen-devel] [PATCH v3 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently
- To: Nadav Amit <namit@xxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
- From: Michael Kelley <mikelley@xxxxxxxxxxxxx>
- Date: Wed, 31 Jul 2019 00:13:57 +0000
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- Cc: Sasha Levin <sashal@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, "linux-hyperv@xxxxxxxxxxxxxxx" <linux-hyperv@xxxxxxxxxxxxxxx>, Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>, "kvm@xxxxxxxxxxxxxxx" <kvm@xxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, "x86@xxxxxxxxxx" <x86@xxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, "virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx" <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, KY Srinivasan <kys@xxxxxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
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- Thread-index: AQHVPc0tyN8NiFudS0OHFO0tHQVBDqbj7WKw
- Thread-topic: [PATCH v3 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently
From: Nadav Amit <namit@xxxxxxxxxx> Sent: Thursday, July 18, 2019 5:59 PM
>
> To improve TLB shootdown performance, flush the remote and local TLBs
> concurrently. Introduce flush_tlb_multi() that does so. Introduce
> paravirtual versions of flush_tlb_multi() for KVM, Xen and hyper-v (Xen
> and hyper-v are only compile-tested).
>
> While the updated smp infrastructure is capable of running a function on
> a single local core, it is not optimized for this case. The multiple
> function calls and the indirect branch introduce some overhead, and
> might make local TLB flushes slower than they were before the recent
> changes.
>
> Before calling the SMP infrastructure, check if only a local TLB flush
> is needed to restore the lost performance in this common case. This
> requires to check mm_cpumask() one more time, but unless this mask is
> updated very frequently, this should impact performance negatively.
>
> Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> Cc: Sasha Levin <sashal@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: linux-hyperv@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Nadav Amit <namit@xxxxxxxxxx>
> ---
> arch/x86/hyperv/mmu.c | 10 +++---
> arch/x86/include/asm/paravirt.h | 6 ++--
> arch/x86/include/asm/paravirt_types.h | 4 +--
> arch/x86/include/asm/tlbflush.h | 8 ++---
> arch/x86/include/asm/trace/hyperv.h | 2 +-
> arch/x86/kernel/kvm.c | 11 +++++--
> arch/x86/kernel/paravirt.c | 2 +-
> arch/x86/mm/tlb.c | 47 ++++++++++++++++++---------
> arch/x86/xen/mmu_pv.c | 11 +++----
> include/trace/events/xen.h | 2 +-
> 10 files changed, 62 insertions(+), 41 deletions(-)
>
For the Hyper-V parts --
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
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