Re: [RFC] 2.3.39 zone balancing

[Andrea Arcangeli <andrea@suse.de>]

On Thu, 13 Jan 2000, Rik van Riel wrote:

>On Wed, 12 Jan 2000, Kanoj Sarcar wrote:
>
>> --- mm/page_alloc.c	Tue Jan 11 11:00:31 2000
>> +++ mm/page_alloc.c	Tue Jan 11 23:59:35 2000
>> +		cumulative += size;
>> +		mask = (cumulative >> 7);
>> +		if (mask < 1) mask = 1;
>> +		zone->pages_low = mask*2;
>> +		zone->pages_high = mask*3;
>>  		zone->low_on_memory = 0;
>
>I think that busier machines probably have a larger need
>for DMA memory than this code fragment will give us. I
>have the gut feeling that we'll want to keep about 512kB
>or more free in the lower 16MB of busy machines...
>
>(if only because such a large amount of free pages in
>such a small part of the address space will give us
>higher-order free pages)

That's only a workaround because the page-freeing mechanism is currently
not aware about fragmentation and about the order of the request we asked
for.

So such code shouldn't be wrote assuming the page-freeing is weak as now.

Supposing it's smart we don't need to take lots of memory free in the dma
zone to allow high order allocations to succeed.

Andrea

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