git only writing 4k at a time

[Haylin Moore <hmoore@qumulo.com>]

Hiya list,

I've been investigating some performance issues around git clones over
network mounts. We have noticed that git is only writing 4k at a time.
These small serial writes are making it such that even though each
write is only a 3ms operation, the total time balloons. Looking around
the source code I found that reftable_writer is initialized by default
(though I cannot find the block_size argument being supplied in my
cursory look) always to DEFAULT_BLOCK_SIZE (4096). Is there some way
to increase/configure this block size such that larger writes happen?
In git/Documentation/config/reftable.adoc this block size is mentioned
in a manner that almost feels configurable, but I'm not sure if this
is just internal for development.

Thanks,
~ Haylin Moore