Mailing List Archive: frame table setup for memory hotplug

frame table setup for memory hotplug

Dec 7, 2012, 8:16 AM

Post #1 of 6 (988 views)

Yunhong,

in c/s 20617:283a5357d196 you modified init_frametable() to
populate the frame table slightly differently for the hotplug
case. I wonder why you did that, because (apart from the bug
already fixed, and the off-by-one bugs I'm having a fix pending
for) I fear you didn't pay attention to the fact that using
pdx_to_page() on something that doesn't really represent the
PDX for a valid page may return a value not validly usable here.

Do you happen to recall what it was that caused you to do that
adjustment in the first place? If you don't, do you have an
environment where you would be able to test an eventual
change of mine (effectively undoing that part of said c/s)?

Thanks, Jan

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Re: frame table setup for memory hotplug [ In reply to ]

yunhong.jiang at intel

Dec 10, 2012, 5:32 AM

Post #2 of 6 (958 views)

Permalink

Jan, sorry for slow response.

IIRC, the reason we do this is because in memory hotplug situation, there will be a very big hole between the address of the memory populated before hot-plug and the memory populated by hot-added memory. (i.e. the added memory started at very high-end address). So instead of setup the frame table for the whole address space, we expand the frame table dynamically after hotplug.

We have the memory hotplug environment, so if you have any patch, I'm glad to test it, or have my colleagues help to test it.

Thanks
--jyh

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Saturday, December 08, 2012 12:16 AM
> To: Jiang, Yunhong
> Cc: xen-devel
> Subject: frame table setup for memory hotplug
>
> Yunhong,
>
> in c/s 20617:283a5357d196 you modified init_frametable() to
> populate the frame table slightly differently for the hotplug
> case. I wonder why you did that, because (apart from the bug
> already fixed, and the off-by-one bugs I'm having a fix pending
> for) I fear you didn't pay attention to the fact that using
> pdx_to_page() on something that doesn't really represent the
> PDX for a valid page may return a value not validly usable here.
>
> Do you happen to recall what it was that caused you to do that
> adjustment in the first place? If you don't, do you have an
> environment where you would be able to test an eventual
> change of mine (effectively undoing that part of said c/s)?
>
> Thanks, Jan
>

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Re: frame table setup for memory hotplug [ In reply to ]

JBeulich at suse

Dec 10, 2012, 5:47 AM

Post #3 of 6 (955 views)

Permalink

>>> On 10.12.12 at 14:32, "Jiang, Yunhong" <yunhong.jiang@intel.com> wrote:
> IIRC, the reason we do this is because in memory hotplug situation, there
> will be a very big hole between the address of the memory populated before
> hot-plug and the memory populated by hot-added memory. (i.e. the added memory
> started at very high-end address). So instead of setup the frame table for the
> whole address space, we expand the frame table dynamically after hotplug.
>
> We have the memory hotplug environment, so if you have any patch, I'm glad
> to test it, or have my colleagues help to test it.

I meanwhile decided to keep the code logically the same, but
testing the patch at
http://lists.xen.org/archives/html/xen-devel/2012-12/msg00793.html
(or the staging/normal trees once it went in/got pushed) would still be
much appreciated.

Thanks, Jan

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Re: frame table setup for memory hotplug [ In reply to ]

yunhong.jiang at intel

Dec 10, 2012, 6:03 AM

Post #4 of 6 (958 views)

Permalink

That hot-plug system is quite difficult to setup. Will let you know when the test is done.

--jyh

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Monday, December 10, 2012 9:48 PM
> To: Jiang, Yunhong
> Cc: xen-devel
> Subject: RE: frame table setup for memory hotplug
>
> >>> On 10.12.12 at 14:32, "Jiang, Yunhong" <yunhong.jiang@intel.com> wrote:
> > IIRC, the reason we do this is because in memory hotplug situation, there
> > will be a very big hole between the address of the memory populated before
> > hot-plug and the memory populated by hot-added memory. (i.e. the added
> memory
> > started at very high-end address). So instead of setup the frame table for the
> > whole address space, we expand the frame table dynamically after hotplug.
> >
> > We have the memory hotplug environment, so if you have any patch, I'm glad
> > to test it, or have my colleagues help to test it.
>
> I meanwhile decided to keep the code logically the same, but
> testing the patch at
> http://lists.xen.org/archives/html/xen-devel/2012-12/msg00793.html
> (or the staging/normal trees once it went in/got pushed) would still be
> much appreciated.
>
> Thanks, Jan

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Re: frame table setup for memory hotplug [ In reply to ]

yunhong.jiang at intel

Dec 14, 2012, 2:07 AM

Post #5 of 6 (951 views)

Permalink

My colleagues helped me to test and seems it's working.

A minor question is, with your patch, we will create all frame table for all potential memory range? That's a bit low efficient IMHO, because there will be large hole between address between pre-populated memory and the new added one.

Thanks
--jyh

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Monday, December 10, 2012 9:48 PM
> To: Jiang, Yunhong
> Cc: xen-devel
> Subject: RE: frame table setup for memory hotplug
>
> >>> On 10.12.12 at 14:32, "Jiang, Yunhong" <yunhong.jiang@intel.com> wrote:
> > IIRC, the reason we do this is because in memory hotplug situation, there
> > will be a very big hole between the address of the memory populated before
> > hot-plug and the memory populated by hot-added memory. (i.e. the added
> memory
> > started at very high-end address). So instead of setup the frame table for the
> > whole address space, we expand the frame table dynamically after hotplug.
> >
> > We have the memory hotplug environment, so if you have any patch, I'm glad
> > to test it, or have my colleagues help to test it.
>
> I meanwhile decided to keep the code logically the same, but
> testing the patch at
> http://lists.xen.org/archives/html/xen-devel/2012-12/msg00793.html
> (or the staging/normal trees once it went in/got pushed) would still be
> much appreciated.
>
> Thanks, Jan

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Re: frame table setup for memory hotplug [ In reply to ]

JBeulich at suse

Dec 17, 2012, 12:43 AM

Post #6 of 6 (951 views)

Permalink

>>> On 14.12.12 at 11:07, "Jiang, Yunhong" <yunhong.jiang@intel.com> wrote:
> My colleagues helped me to test and seems it's working.

Thanks!

> A minor question is, with your patch, we will create all frame table for all
> potential memory range? That's a bit low efficient IMHO, because there will
> be large hole between address between pre-populated memory and the new added
> one.

No, we won't. The only thing we will fully populate is the super page
frame table (if enabled in the first place), which is better than not
populating its ranges covering hotplug memory at all (as was the
case before the patch); I'm certainly not against making this more
efficient, but that would imo need to be done by someone being
able to actually test the code paths needing modification.

Jan

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