From: David Gibson <david@gibson.dropbear.id.au>
To: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: paulus@samba.org, mpe@ellerman.id.au, benh@kernel.crashing.org,
aik@ozlabs.ru, lvivier@redhat.com, thuth@redhat.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFCv2 9/9] pseries: Automatically resize HPT for memory hot add/remove
Date: Mon, 1 Feb 2016 21:55:24 +1100 [thread overview]
Message-ID: <20160201105524.GI23043@voom.redhat.com> (raw)
In-Reply-To: <56AF1CA2.30603@linux.vnet.ibm.com>
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On Mon, Feb 01, 2016 at 02:21:46PM +0530, Anshuman Khandual wrote:
> On 01/29/2016 10:54 AM, David Gibson wrote:
> > #ifdef CONFIG_MEMORY_HOTPLUG
> > +void resize_hpt_for_hotplug(unsigned long new_mem_size)
> > +{
> > + unsigned target_hpt_shift;
> > +
> > + if (!ppc_md.resize_hpt)
> > + return;
> > +
> > + target_hpt_shift = htab_shift_for_mem_size(new_mem_size);
> > +
> > + /*
> > + * To avoid lots of HPT resizes if memory size is fluctuating
> > + * across a boundary, we deliberately have some hysterisis
>
>
> What do you mean by 'memory size is fluctuating across a boundary' ?
> Through memory hotplug interface ? Why some one will do that ?
I was thinking it might be possible to have some management system
that automatically adjusts memory size based on load, and if that
happened to land on a boundary you could get nasty behaviour.
> I
> can understand why we dont have this check in the sysfs debug path
> as we would like to test any memory HPT re sizing scenario we want
> in any sequence of increase or decrease we want.
>
> Overall the RFC V2 looks pretty good. Looking forward to see the
> host side of the code for this feature.
The qemu host side has been posted to qemu-devel@nongnu.org already.
I haven't started on a KVM HV implementation yet.
--
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:[~2016-02-01 11:07 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 5:23 [RFCv2 0/9] PAPR hash page table resizing (guest side) David Gibson
2016-01-29 5:23 ` [RFCv2 1/9] memblock: Don't mark memblock_phys_mem_size() as __init David Gibson
2016-02-01 5:50 ` Anshuman Khandual
2016-02-08 2:46 ` Paul Mackerras
2016-01-29 5:23 ` [RFCv2 2/9] arch/powerpc: Clean up error handling for htab_remove_mapping David Gibson
2016-02-01 5:54 ` Anshuman Khandual
2016-02-08 2:48 ` Paul Mackerras
2016-01-29 5:23 ` [RFCv2 3/9] arch/powerpc: Handle removing maybe-present bolted HPTEs David Gibson
2016-02-01 5:58 ` Anshuman Khandual
2016-02-02 1:08 ` David Gibson
2016-02-02 13:49 ` Denis Kirjanov
2016-02-08 2:54 ` Paul Mackerras
2016-02-09 0:43 ` David Gibson
2016-01-29 5:23 ` [RFCv2 4/9] arch/powerpc: Clean up memory hotplug failure paths David Gibson
2016-02-01 6:29 ` Anshuman Khandual
2016-02-02 15:04 ` Nathan Fontenot
2016-02-03 4:31 ` David Gibson
2016-02-08 5:47 ` Paul Mackerras
2016-01-29 5:23 ` [RFCv2 5/9] arch/powerpc: Split hash page table sizing heuristic into a helper David Gibson
2016-02-01 7:04 ` Anshuman Khandual
2016-02-02 1:04 ` David Gibson
2016-02-04 10:56 ` Anshuman Khandual
2016-02-08 5:57 ` Paul Mackerras
2016-01-29 5:24 ` [RFCv2 6/9] pseries: Add hypercall wrappers for hash page table resizing David Gibson
2016-02-01 7:11 ` Anshuman Khandual
2016-02-02 0:58 ` David Gibson
2016-02-04 11:11 ` Anshuman Khandual
2016-02-07 22:33 ` David Gibson
2016-02-08 5:58 ` Paul Mackerras
2016-01-29 5:24 ` [RFCv2 7/9] pseries: Add support for hash " David Gibson
2016-02-01 8:31 ` Anshuman Khandual
2016-02-01 11:04 ` David Gibson
2016-02-08 5:59 ` Paul Mackerras
2016-01-29 5:24 ` [RFCv2 8/9] pseries: Advertise HPT resizing support via CAS David Gibson
2016-02-01 8:36 ` Anshuman Khandual
2016-02-08 6:00 ` Paul Mackerras
2016-01-29 5:24 ` [RFCv2 9/9] pseries: Automatically resize HPT for memory hot add/remove David Gibson
2016-02-01 8:51 ` Anshuman Khandual
2016-02-01 10:55 ` David Gibson [this message]
2016-02-08 6:01 ` Paul Mackerras
2016-02-01 5:50 ` [RFCv2 0/9] PAPR hash page table resizing (guest side) Anshuman Khandual
2016-02-02 0:57 ` David Gibson
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