Ar Gwe, 2006-09-22 am 21:10 +0200, ysgrifennodd Andi Kleen:
> We already have that scheme. Any existing driver should be already converted
> away from GFP_DMA towards dma_*/pci_*. dma_* knows all the magic
> how to get memory for the various ranges. No need to mess up the
> main allocator.
Add an isa_device class and that'll fall into place nicely. isa_alloc_*
will end up asking for 20bit DMA and it will work nicely.
> Anyways, i suppose what could be added as a fallback would be a
> really_slow_brute_force_try_to_get_something_in_this_range() allocator
Implementation detail although I note that the defrag/antifrag proposal
made at the vm summit would mean it mostly come out for free. If we have
an isa_dma_* API then the detail is platform specific.
> that basically goes through the buddy lists freeing in >O(1)
> and does some directed reclaim, but that would likely be a separate
> path anyways and not need your new structure to impact the O(1)
> allocator.
Just search within the candidate 4MB (or whatever it is these days)
chunks.
> I am still unconvinced of the real need. The only gaping hole was
> GFP_DMA32, which we fixed already.
Various devices are 30 and 31bit today - some broadcom for example.
> Ok there is aacraid with its weird 2GB limit,
> Ok now I'm sure someone will come up with a counter example (hi Alan), but:
> - Does the device really need more than 16MB?
> - How often is it used on systems with >1/2GB with a 64bit kernel?
> [consider that 64bit kernels don't support ISA]
> - How many users of that particular thing around?
Ok the examples I know about are
- ESS Maestro series audio - PCI, common on 32bit boxes a few years ago,
no longer shipped and unlikely to be met on 64bit. Also slow allocations
is fine.
- Some aacraid, mostly only for control structures. Those found on 64bit
are probably fine with slow alloc.
- Broadcom stuff - not sure if 30 or 31bit, around today and on 64bit
- Floppy controller
> I think my point stands.
I think its worthy of discussion.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
