Re: [PATCH v3 3/5] page_alloc: Introduce zone_movable_limit[] to keep movable limit for nodes

On Wed, 2012-12-12 at 17:09 +0800, Tang Chen wrote:

On 12/12/2012 08:49 AM, Jiang Liu wrote:

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This patch introduces a new array zone_movable_limit[] to store the
ZONE_MOVABLE limit from movablecore_map boot option for all nodes.
The function sanitize_zone_movable_limit() will find out to which
node the ranges in movable_map.map[] belongs, and calculates the
low boundary of ZONE_MOVABLE for each node.

What's the difference between zone_movable_limit[nid] and
zone_movable_pfn[nid]?

zone_movable_limit[] is a temporary storage for zone_moveable_pfn[].
It's used to handle a special case if user specifies both movablecore_map
and movablecore/kernelcore on the kernel command line.

Hi Simon, Liu,

Sorry for the late and thanks for your discussion. :)

As Liu said, zone_movable_limit[] is a temporary array for calculation.

If users specified movablecore_map option, zone_movable_limit[] holds
the lowest pfn of ZONE_MOVABLE limited by movablecore_map option. It is 
constant, won't change.

Please refer to find_zone_movable_pfns_for_nodes() in patch4, you will
see that zone_moveable_pfn[] will be changed each time kernel area
increases.

So when kernel area increases on node i, zone_moveable_pfn[i] will
increase. And if zone_moveable_pfn[i] > zone_movable_limit[i], we should
stop allocate memory for kernel on node i. Here, I give movablecore_map 
higher priority than kernelcore/movablecore.

And also, I tried to use zone_moveable_pfn[] to store limits. But when
calculating the kernel area, I still have to store the limits in
temporary variables. I think the code was ugly. So I added an new array.

Thanks. :)

Thanks for your clarify. 

Enable PAE on x86 32bit kernel, 8G memory, movablecore=6.5G

[    0.000000] 8304MB HIGHMEM available.
[    0.000000] 885MB LOWMEM available.
[    0.000000]   mapped low ram: 0 - 375fe000
[    0.000000]   low ram: 0 - 375fe000
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x00010000-0x00ffffff]
[    0.000000]   Normal   [mem 0x01000000-0x375fdfff]
[    0.000000]   HighMem  [mem 0x375fe000-0x3e5fffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x00010000-0x0009cfff]
[    0.000000]   node   0: [mem 0x00100000-0x1fffffff]
[    0.000000]   node   0: [mem 0x20200000-0x3fffffff]
[    0.000000]   node   0: [mem 0x40200000-0xb69cbfff]
[    0.000000]   node   0: [mem 0xb6a46000-0xb6a47fff]
[    0.000000]   node   0: [mem 0xb6b1c000-0xb6cfffff]
[    0.000000]   node   0: [mem 0x00000000-0x3e5fffff]
[    0.000000] On node 0 totalpages: 2051391
[    0.000000] free_area_init_node: node 0, pgdat c0c26a80,
node_mem_map
f19de200
[    0.000000]   DMA zone: 32 pages used for memmap
[    0.000000]   DMA zone: 0 pages reserved
[    0.000000]   DMA zone: 3949 pages, LIFO batch:0
[    0.000000]   Normal zone: 1740 pages used for memmap
[    0.000000]   Normal zone: 220466 pages, LIFO batch:31
[    0.000000]   HighMem zone: 16609 pages used for memmap
[    0.000000]   HighMem zone: 1808595 pages, LIFO batch:31

Why zone movable disappear?



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