From: David Gibson <david@gibson.dropbear.id.au>
To: Daniel Henrique Barboza <danielhb413@gmail.com>
Cc: qemu-ppc@nongnu.org, Igor Mammedov <imammedo@redhat.com>,
John Snow <jsnow@redhat.com>,
Eduardo Habkost <ehabkost@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [PATCH 02/10] numa: introduce MachineClass::forbid_asymmetrical_numa
Date: Tue, 25 Aug 2020 21:12:08 +1000 [thread overview]
Message-ID: <20200825111208.GH4734@yekko.fritz.box> (raw)
In-Reply-To: <98728fe4-1262-6be2-8dd1-1b38ffbe81e9@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1705 bytes --]
On Tue, Aug 25, 2020 at 06:56:46AM -0300, Daniel Henrique Barboza wrote:
>
>
> On 8/24/20 8:49 PM, David Gibson wrote:
> > On Mon, Aug 24, 2020 at 08:45:12AM -0300, Daniel Henrique Barboza wrote:
> > >
> > >
>
> [...]
>
> > > > > LOPAPR support a somewhat asymmetrical NUMA setup in its current
> > > > > form,
> > > >
> > > > Huh, I didn't even realize that. What's the mechanism?
> > >
> > > LOPAPR mentions that a single resource/node can have multiple associativity
> > > arrays. The idea is to contemplate the situations where the node has
> > > more than one connection with the board.
> > >
> > > I say "somewhat" because, right after mentioning that, the spec also says that
> > > the OS should consider that the distance between two nodes must always be
> > > the shortest one of all available arrays. I'll copy/paste the except here
> > > (end of section 15.2, "Numa Resource Associativity":
> >
> > Ah. I didn't think that's what "asymmetric NUMA" meant... but come to
> > think of it, I'm not very sure about that.
>
>
> This was a poor attempt of my part to cut PAPR some slack.
>
> TBH, even if current PAPR allows for some form of NUMA asymmetry, I don't think
> it's worth implementing at all. It'll be more complexity on top of what I
> already added here, and the best case scenario will be the kernel ignoring it
> (worst case - kernel blowing it up because we're adding more associativity
> arrays in each CPU and so on).
Yes, I agree.
--
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: 833 bytes --]
next prev parent reply other threads:[~2020-08-25 11:19 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-14 20:54 [PATCH 00/10] pseries NUMA distance rework Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 01/10] hw: add compat machines for 5.2 Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 02/10] numa: introduce MachineClass::forbid_asymmetrical_numa Daniel Henrique Barboza
2020-08-20 1:17 ` David Gibson
2020-08-20 2:11 ` Eduardo Habkost
2020-08-20 4:15 ` David Gibson
2020-08-20 10:33 ` Daniel Henrique Barboza
2020-08-20 14:29 ` Igor Mammedov
2020-08-20 16:51 ` Eduardo Habkost
2020-08-21 8:55 ` Igor Mammedov
2020-08-21 12:47 ` Daniel Henrique Barboza
2020-08-24 6:08 ` David Gibson
2020-08-24 11:45 ` Daniel Henrique Barboza
2020-08-24 23:49 ` David Gibson
2020-08-25 9:56 ` Daniel Henrique Barboza
2020-08-25 11:12 ` David Gibson [this message]
2020-09-23 15:21 ` John Snow
2020-08-14 20:54 ` [PATCH 03/10] spapr: robustify NVLink2 NUMA node logic Daniel Henrique Barboza
2020-08-20 2:14 ` David Gibson
2020-08-26 21:49 ` Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 04/10] spapr: add spapr_machine_using_legacy_numa() helper Daniel Henrique Barboza
2020-08-20 2:15 ` David Gibson
2020-08-14 20:54 ` [PATCH 05/10] spapr: make ibm, max-associativity-domains scale with user input Daniel Henrique Barboza
2020-08-20 2:55 ` [PATCH 05/10] spapr: make ibm,max-associativity-domains " David Gibson
2020-08-26 21:17 ` Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 06/10] spapr: allow 4 NUMA levels in ibm, associativity-reference-points Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 07/10] spapr: create helper to set ibm,associativity Daniel Henrique Barboza
2020-08-20 3:00 ` David Gibson
2020-08-20 10:39 ` Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 08/10] spapr: introduce SpaprMachineClass::numa_assoc_domains Daniel Henrique Barboza
2020-08-20 4:26 ` David Gibson
2020-08-26 20:06 ` Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 09/10] spapr: consider user input when defining spapr guest NUMA Daniel Henrique Barboza
2020-08-14 20:54 ` [PATCH 10/10] specs/ppc-spapr-numa: update with new NUMA support Daniel Henrique Barboza
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=20200825111208.GH4734@yekko.fritz.box \
--to=david@gibson.dropbear.id.au \
--cc=danielhb413@gmail.com \
--cc=ehabkost@redhat.com \
--cc=imammedo@redhat.com \
--cc=jsnow@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=qemu-ppc@nongnu.org \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).