hole punching performance

["Bradley C. Kuszmaul" <kuszmaul@xxxxxxxxx>]

If I use hole-punching, what will happen to the performance of my application?

I have a multithreaded application that creates large files (many
gigabytes per file).  The application sometimes wants to punch holes
(say 1 megabyte in size).

On Redhat 6, I've measured that punching holes requires about 2ms
(this with a battery-backed up RAID controller), which is slower than
I was hoping for, but it's probably OK.  The throughput is only about
2ms per hole-punch even if I have lots of threads punching holes in
lots of different files at the same time.

The question I have:  What will happen to the performance of other
threads doing read() and write() operations?  Will hole-punching slow
down the other read() and write() operations running in other threads?

I'm willing to do some measurements, but I'm not sure what I should be
watching out for, so if you can educate me about it, I'd appreciate
it.

-Bradley