Giuliano Pochini wrote:

quoted

quoted

An alternate approach might be to change the way the scheduler splits
things. That is, rather than marking I/O read vs write and scheduling
based on that, add a flag bit to mark them all sync vs async since
that's the distinction we actually care about. The normal paths can
all do read+sync and write+async, but you can now do things like
marking your truncate writes sync and readahead async.

quoted

That will be worth investigating to see if the complexity is worth it.
I think from a disk point of view, we still want to split batches between
reads and writes. Could be wrong.

Yes, sync vs async is a better way to classify io requests than
read vs write and it's more correct from OS point of view. IMHO
it's not more complex then now. Just replace r/w with sy/as and
it will work.

We probably wouldn't want to go that far as you obviously can
only merge reads with reads and writes with writes, a flag would
be fine. We have to get the basics working first though ;)

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