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SubjectRe: [PATCH] 2.3.23pre4 - DMA fix, boot failure on ABIT BP6 and page_alloc.c improvements

On Wed, 20 Oct 1999, Benjamin C.R. LaHaise wrote:

> Below are three patches. The first to setup.c fixes a problem my BP6 was
> triggering in the new E820/bootmem code -- one of the memory regions was a
> paltry 1KB in size, and it wasn't being skipped properly.

(cool)

> The second to bootmem.c fixes the problem with all memory being marked as
> DMA.

(embarrasing! i managed to put two serious bugs into a twoliner, hm.)

> The third to page_alloc.c is not an essential fix, but rather a forward
> port of a patch in 2.2.13 that splits GFP_DMA pages into a separate list
> from non-DMA pages. This helps keep the system's DMA pool at a higher
> steady state since the last of the DMAable pages will only be consumed by
> atomic allocations. Personally, I think it makes the high memory stuff
> look a bit more tidy =)
>
> This patch is against 2.3.23pre4 plus Ingo's highmem-2.3.23-D3 patch.

nice cleanups, and this now looks more and more like a zoned allocator.

there is one detail that i think still needs fixing: all three zones now
have basically the same bitmap size, which can take up a considerable
amount of memory:

DMA: xxx.........................................
normal mem: ...xxxxxxxxxxxxxxxxxxxxxx...................
highmem: .........................xxxxxxxxxxxxxxxxxxx

the more zones we have, the more vastage - currently bitmaps are three
times as big as they need to be.

We do not need the dynamic overhead of an area->offset though, we can just
tweak frea_area[][].map's address in a way that offsets it exactly in such
a way that makes page indices universally correct in the current sense.
And not memset() all of free_area[][].map when initializing :)

-- mingo


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