I will look into it. It might have to wait for the next release, but I
will see what I can do. I wanted have a pre-release out so I could do the
release on Halloween, but looks like it might be Halloween until I get the
pre-release out with release to follow soon after (depends on issues
raised).
Jeremy
On Mon, Oct 25, 2021, 2:52 PM E. Auer wrote:
>
> Hi Jeremy,
>
> a last minute request for the new kernel release:
>
> In context of the patch for significant I/O speed improvements
> by only splitting transfers around DMA boundaries for drives
> where that actually is needed, based on the int 13.48 flags,
>
> please add a config sys option to override the int 13.48 answer
> into either "always avoid DMA boundaries" or "always assume DMA
> boundaries are no problem" for all fixed disks (0x80 and up).
>
> Background: MS DOS, predating the int 13.4x extensions, probably
> defaults to never avoiding DMA boundaries for fixed disks and
> always avoiding them for floppy. So the config sys flag can give
> us MS DOS speed and behavior even when using BIOSes which fail
> to properly report their ability to transparently handle any DMA
> boundary issues. We would needlessly lose I/O speed otherwise.
>
> The other option, always avoiding DMA boundaries, would allow
> the user to switch back to old FreeDOS behaviour, for example
> for benchmark comparisons or for cases where the BIOS claims
> to be DMA boundary safe, but actually messes up handling there.
>
> Thanks :-) As said, the ability to either avoid or not avoid DMA
> boundaries would make a big difference for I/O speed. I think it
> was Tom who proposed the patch which made us int 13.48 aware :-)
>
> Regards, Eric
>
> PS: I think it is NOT necessary to have similar options for
> individual drive numbers, because any mismatch between the
> reported and actual abilities will usually affect all disks
> of the same BIOS and having 2+ broken disk BIOSes is uncommon.
>
>
>
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