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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