From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: linux-mm <linux-mm@kvack.org>, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/2] Register bootmem pages at boot on powerpc
Date: Tue, 13 Aug 2013 07:59:34 +1000 [thread overview]
Message-ID: <1376344774.32100.185.camel@pasglop> (raw)
In-Reply-To: <520952C9.3060101@linux.vnet.ibm.com>
On Mon, 2013-08-12 at 16:25 -0500, Nathan Fontenot wrote:
> On 08/12/2013 04:13 PM, Benjamin Herrenschmidt wrote:
> > On Mon, 2013-08-12 at 08:01 -0500, Nathan Fontenot wrote:
> >>> Can you tell me a bit more, the above makes me nervous...
> >>
> >> Ok, I agree. that message isn't quite right.
> >>
> >> What I wanted to convey is that memory hotplug is not fully supported
> >> on powerpc with SPARSE_VMEMMAP enabled.. Perhaps the message should read
> >> "Memory hotplug is not fully supported for bootmem info nodes".
> >>
> >> Thoughts?
> >
> > Since SPARSE_VMEMMAP is our default and enabled in our distros, that mean
> > that memory hotplug isn't fully supported for us in general ?
>
> Actually... We have had the distros (at least SLES 11 and RHEL 6 releases)
> disable SPARSE_VMEMMAP in their releases.
Yuck ! That has a significant impact on performances... Additionally our
VFIO implementation for KVM requires SPARSE_VMEMMAP. Why is it that this
was never fixed in all these years ?
> >
> > What do you mean by "not fully supported" ? What precisely is missing ?
> > What will happen if one tries to plug or unplug memory?
>
> I don't know everything that is missing, but there are several routines
> that need to be defined for power to support memory hotplug with SPARSE_VMEMMAP.
>
> >
> > Shouldn't we fix it ?
>
> Working on it, but it's not there yet.
Ok, thanks.
Cheers,
Ben.
> >
> > Cheers,
> > Ben.
> >
> >
>
> --
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prev parent reply other threads:[~2013-08-12 21:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-09 15:29 [PATCH 0/2] Correct memory hotplug remove Nathan Fontenot
2013-08-09 15:30 ` [PATCH 1/2] Mark memory resources as busy Nathan Fontenot
2013-08-09 15:32 ` [PATCH 2/2] Register bootmem pages at boot on powerpc Nathan Fontenot
2013-08-12 0:19 ` Benjamin Herrenschmidt
2013-08-12 13:01 ` Nathan Fontenot
2013-08-12 21:13 ` Benjamin Herrenschmidt
2013-08-12 21:25 ` Nathan Fontenot
2013-08-12 21:59 ` Benjamin Herrenschmidt [this message]
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