All of lore.kernel.org
 help / color / mirror / Atom feed
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>

[-- Attachment #1: Type: text/plain, Size: 1511 bytes --]

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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20160201105524.GI23043@voom.redhat.com \
    --to=david@gibson.dropbear.id.au \
    --cc=aik@ozlabs.ru \
    --cc=benh@kernel.crashing.org \
    --cc=khandual@linux.vnet.ibm.com \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=lvivier@redhat.com \
    --cc=mpe@ellerman.id.au \
    --cc=paulus@samba.org \
    --cc=thuth@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.