From: David Gibson <david@gibson•dropbear.id.au>
To: Paul Mackerras <paulus@ozlabs•org>
Cc: aik@ozlabs•ru, benh@kernel•crashing.org,
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: Thu, 25 Aug 2016 13:57:29 -0400 [thread overview]
Message-ID: <20160825175729.GC2225@littlecatz> (raw)
In-Reply-To: <20160825123834.GB4815@fergus.ozlabs.ibm.com>
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On Thu, Aug 25, 2016 at 10:38:34PM +1000, Paul Mackerras wrote:
> 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).
> >
> > 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.
>
> I have finally managed to have a close look at this series. The
> approach and implementation seem basically sane,
Ok, good to know.
> though I think the
> rehash function could be optimized a bit. I also have an optimized
> implementation of hpte_page_size() and hpte_base_page_size() which
> should be a lot quicker than the 2d linear (areal?) search which we do
> at present.
Ok, sounds like with those optimizations this approach might be good
enough. I aim to send a revised version of these some time after the
RHEL 7.3 crunch.
In the meantime, any word on the PAPR proposal?
--
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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prev parent reply other threads:[~2016-08-25 18:03 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 ` [RFCv3 00/17] PAPR HPT resizing, guest & host side David Gibson
2016-08-25 12:38 ` Paul Mackerras
2016-08-25 17:57 ` David Gibson [this message]
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