Re: [PATCH part5 0/7] Arrange hotpluggable memory as ZONE_MOVABLE.

[Tang Chen <tangchen@cn.fujitsu.com>]

On 08/16/2013 04:28 AM, Yinghai Lu wrote:
......
>>
>> So, we still need reordering, and put a new requirement that all earlier
>> allocations must be small...
>>
>> I think the root of this issue is that ACPI init point is not early
>> enough in the boot sequence.  If it were much earlier already, the whole
>> thing would have been very simple.  We are now trying to workaround this
>> issue in the mblock code (which itself is a fine idea), but this ACPI
>> issue still remains and similar issues may come up again in future.
>>
>> For instance, ACPI SCPR/DBGP/DBG2 tables allow the OS to initialize
>> serial console/debug ports at early boot time.  The earlier it can be
>> initialized, the better this feature will be.  These tables are not
>> currently used by Linux due to a licensing issue, but it could be
>> addressed some time soon.  As platforms becoming more complex&  legacy
>> free, the needs of ACPI tables will increase.
>>
>> I think moving up the ACPI init point earlier is a good direction.
>
> Good point.
>
> If we put acpi_initrd_override in BRK, and can more acpi_boot_table_init()
> much early.

Hi yinghai, toshi,

Since I brought up this issue, it has been a long time. And there were a 
lot
of different solutions came up. No solution is perfect enough for everyone.
I have tried a lot, and most of them failed. But I think most of the things
cannot be seen clearly without a real patch posted. Many good ideas came up
during patch reviewing.

So I think I'm going to try as many ways as possible.  :)


Parsing SRAT earlier is what I want to do in the very beginning indeed. And
now, seems that moving the whole acpi table installation and overriding 
earlier
will bring us much more benefits. I have tried this without moving up
acpi_initrd_override in my part1 patch-set. But not in the way Yinghai 
mentioned
above.

Seeing from the code, there are 5 pages in BRK for page tables.

   81 /* need 4 4k for initial PMD_SIZE, 4k for 0-ISA_END_ADDRESS */
   82 #define INIT_PGT_BUF_SIZE       (5 * PAGE_SIZE)
   83 RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE);

By "put acpi_initrd_override in BRK", do you mean increase the BRK by 
default ?

Thanks.

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