From: David Gibson <david@gibson.dropbear.id.au>
To: paulus@samba.org, aik@ozlabs.ru, benh@kernel.crashing.org
Cc: bharata@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
michael@ellerman.id.au
Subject: Re: [RFCv3 00/17] PAPR HPT resizing, guest & host side
Date: Mon, 21 Mar 2016 16:46:34 +1100 [thread overview]
Message-ID: <20160321054634.GK23586@voom.redhat.com> (raw)
In-Reply-To: <1458532404-21258-1-git-send-email-david@gibson.dropbear.id.au>
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On Mon, Mar 21, 2016 at 02:53:07PM +1100, David Gibson wrote:
> This is an implementation of the kernel parts of the PAPR hashed page
> table (HPT) resizing extension.
>
> It contains a complete guest-side implementation - or as complete as
> it can be until we have a final PAPR change.
>
> It also contains a draft host side implementation for KVM HV (the KVM
> PR and TCG host-side implementations live in qemu). This works, but
> is very slow in the critical section (where the guest must be
> stopped). It is significantly slower than the TCG/PR implementation;
> unusably slow for large hash tables (~2.8s for a 1G HPT).
Since posting this, I've managed to bring this down to ~570ms for a 1G
HPT. Still slow, but much better. The optimization to do this was to
skip rehashing an HPTE if neither VALID|ABSENT are set *before*
locking the HPTE. I believe this is safe, since nothing should be
able to add new VALID|ABSENT HPTEs while the guest is stopped.
>
> I'm still looking into what's the cause of the slowness, and I'm not
> sure yet if the current approach can be tweaked to be fast enough, or
> if it will require a new approach.
>
> Changes since RFCv2:
> * Completely new approach to handling KVM HV implementation. Much
> simpler synchronization requirements, but also slower
> * Rebase to latest Linus' tree
> * Changed number for capability, so as not to collide
> * Host side now actually works
>
> David Gibson (17):
> pseries: Add hypercall wrappers for hash page table resizing
> pseries: Add support for hash table resizing
> pseries: Advertise HPT resizing support via CAS
> pseries: Automatically resize HPT for memory hot add/remove
> powerpc/kvm: Corectly report KVM_CAP_PPC_ALLOC_HTAB
> powerpc/kvm: Add capability flag for hashed page table resizing
> powerpc/kvm: Rename kvm_alloc_hpt() for clarity
> powerpc/kvm: Gather HPT related variables into sub-structure
> powerpc/kvm: Don't store values derivable from HPT order
> powerpc/kvm: Split HPT allocation from activation
> powerpc/kvm: Allow KVM_PPC_ALLOCATE_HTAB ioctl() to change HPT size
> powerpc/kvm: Create kvmppc_unmap_hpte_helper()
> powerpc/kvm: KVM-HV HPT resizing stub implementation
> powerpc/kvm: Outline of KVM-HV HPT resizing implementation
> powerpc/kvm: KVM-HV HPT resizing, preparation path
> powerpc/kvm: HVM-HV HPT resizing, commit path
> powerpc/kvm: Advertise availablity of HPT resizing on KVM HV
>
> arch/powerpc/include/asm/firmware.h | 5 +-
> arch/powerpc/include/asm/hvcall.h | 2 +
> arch/powerpc/include/asm/kvm_book3s.h | 12 +-
> arch/powerpc/include/asm/kvm_book3s_64.h | 15 +
> arch/powerpc/include/asm/kvm_host.h | 17 +-
> arch/powerpc/include/asm/kvm_ppc.h | 11 +-
> arch/powerpc/include/asm/machdep.h | 1 +
> arch/powerpc/include/asm/plpar_wrappers.h | 12 +
> arch/powerpc/include/asm/prom.h | 1 +
> arch/powerpc/include/asm/sparsemem.h | 1 +
> arch/powerpc/kernel/prom_init.c | 2 +-
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 626 ++++++++++++++++++++++++------
> arch/powerpc/kvm/book3s_hv.c | 37 +-
> arch/powerpc/kvm/book3s_hv_builtin.c | 8 +-
> arch/powerpc/kvm/book3s_hv_rm_mmu.c | 68 ++--
> arch/powerpc/kvm/powerpc.c | 17 +-
> arch/powerpc/mm/hash_utils_64.c | 57 +++
> arch/powerpc/mm/mem.c | 4 +
> arch/powerpc/platforms/pseries/firmware.c | 1 +
> arch/powerpc/platforms/pseries/lpar.c | 110 ++++++
> include/uapi/linux/kvm.h | 1 +
> 21 files changed, 825 insertions(+), 183 deletions(-)
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2016-03-21 5:45 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-21 3:53 [RFCv3 00/17] PAPR HPT resizing, guest & host side David Gibson
2016-03-21 3:53 ` [RFCv3 01/17] pseries: Add hypercall wrappers for hash page table resizing David Gibson
2016-03-21 3:53 ` [RFCv3 02/17] pseries: Add support for hash " David Gibson
2016-03-21 3:53 ` [RFCv3 03/17] pseries: Advertise HPT resizing support via CAS David Gibson
2016-03-21 3:53 ` [RFCv3 04/17] pseries: Automatically resize HPT for memory hot add/remove David Gibson
2016-03-21 3:53 ` [RFCv3 05/17] powerpc/kvm: Corectly report KVM_CAP_PPC_ALLOC_HTAB David Gibson
2016-03-21 3:53 ` [RFCv3 06/17] powerpc/kvm: Add capability flag for hashed page table resizing David Gibson
2016-03-21 3:53 ` [RFCv3 07/17] powerpc/kvm: Rename kvm_alloc_hpt() for clarity David Gibson
2016-03-21 3:53 ` [RFCv3 08/17] powerpc/kvm: Gather HPT related variables into sub-structure David Gibson
2016-03-21 3:53 ` [RFCv3 09/17] powerpc/kvm: Don't store values derivable from HPT order David Gibson
2016-03-21 3:53 ` [RFCv3 10/17] powerpc/kvm: Split HPT allocation from activation David Gibson
2016-03-21 3:53 ` [RFCv3 11/17] powerpc/kvm: Allow KVM_PPC_ALLOCATE_HTAB ioctl() to change HPT size David Gibson
2016-03-21 3:53 ` [RFCv3 12/17] powerpc/kvm: Create kvmppc_unmap_hpte_helper() David Gibson
2016-03-21 3:53 ` [RFCv3 13/17] powerpc/kvm: KVM-HV HPT resizing stub implementation David Gibson
2016-03-21 3:53 ` [RFCv3 14/17] powerpc/kvm: Outline of KVM-HV HPT resizing implementation David Gibson
2016-03-21 3:53 ` [RFCv3 15/17] powerpc/kvm: KVM-HV HPT resizing, preparation path David Gibson
2016-03-21 3:53 ` [RFCv3 16/17] powerpc/kvm: HVM-HV HPT resizing, commit path David Gibson
2016-03-21 3:53 ` [RFCv3 17/17] powerpc/kvm: Advertise availablity of HPT resizing on KVM HV David Gibson
2016-03-21 5:46 ` David Gibson [this message]
2016-08-25 12:38 ` [RFCv3 00/17] PAPR HPT resizing, guest & host side Paul Mackerras
2016-08-25 17:57 ` David Gibson
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