On 03/19/2015 08:17 PM, Christoph Hellwig wrote:
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In addition to the options there's also a time line.  At least for the
short term where we want to get something going 1a seems like the
absolutely be option.  It works perfectly fine for the lots of small
capacity dram-like nvdimms, and it works funtionally fine for the
special huge ones, although the resource use for it is highly annoying.
If it turns out to be too annoying we can also offer a no I/O possible
option for them in the short run.

Finally some voice in the dessert.

In the long run option 2) sounds like a good plan to me, but not as a
parallel I/O path, but as the main one.  Doing so will in fact give us
options to experiment with 3).  Given that we're moving towards an
increasinly huge page using world replacing the good old struct page
with something extent-like and/or temporary might be needed for dram
as well in the future.

Why ? why not just make page mean page_size(page) and mostly even that
is not needed.

Any changes to bio will only solve bio. And will push the problem to
the next subsystem.

Fix the PAGE_SIZE problem and you fixed it for all subsystems, not only
bio. And I believe it is the smaller change by far.

Because in most places PAGE_SIZE just means MIN_PAGE_SIZE when we try
calculate some array sizes for storage of a given "io-length", this
is surly 4k, but then when the actual run time is preformed we usually
have a length specifier like bv_len. (And the few places that do not are
easy to fix I believe)

Thanks
Boaz