Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management

2 messages, 2 authors, 2011-06-30 · open the first message on its own page

Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management

From: Andi Kleen <hidden>
Date: 2011-06-29 20:12:26

Dave Hansen [off-list ref] writes:
It's also going to be a pain to track kernel references.  On x86, our
Even if you tracked them what would you do with them?

It's quite hard to stop using arbitary kernel memory (see all the dancing
memory-failure does) 

You need to track the direct accesses to user data which happens
to be accessed through the direct mapping.

Also it will be always unreliable because this all won't track DMA.
For that you would also need to track in the dma_* infrastructure,
which will likely get seriously expensive.

-Andi

-- 
ak at linux.intel.com -- Speaking for myself only

Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management

From: Ankita Garg <hidden>
Date: 2011-06-30 05:11:41

Hi,

On Wed, Jun 29, 2011 at 01:11:00PM -0700, Andi Kleen wrote:
Dave Hansen [off-list ref] writes:
quoted
It's also going to be a pain to track kernel references.  On x86, our
As Vaidy mentioned, we are only looking at memory being either allocated
or free, as a way to evacuate it. Tracking memory references, no doubt,
is a difficult proposition and might involve a lot of overhead.
 
Even if you tracked them what would you do with them?

It's quite hard to stop using arbitary kernel memory (see all the dancing
memory-failure does) 

You need to track the direct accesses to user data which happens
to be accessed through the direct mapping.

Also it will be always unreliable because this all won't track DMA.
For that you would also need to track in the dma_* infrastructure,
which will likely get seriously expensive.
-- 
Regards,
Ankita Garg (ankita at in.ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India
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