Hi Alan,
When looking at the FileChannel.map() method, it seems that it will not
write "e" 4 billion times. Instead, it only extends the file size to
testSize+10. It uses ftruncate() in linux and uses SetFilePointer() in
Windows, which causes the file offset different on different platforms.
But the performance should be good. On windows, this test runs for
around 0.14 seconds in jprt machines. Thanks!
-Dan
On Thu 21 Nov 2013 11:51:28 AM PST, Alan Bateman wrote:
On 21/11/2013 17:02, Dan Xu wrote:
Hi Alan,
I think the map is used to enlarge the size of the largeFile to
testSize + 10. In initTestFile(), it initiates the file with size 10.
My understanding is that it avoids writing large amount of data into
the largeFile by using the map. Thanks!
-Dan
Okay, I guess I was really just wondering about the reliability on
Windows as sometimes tests that use memory mapped files are
troublesome when it comes to clean-up after the test. Also as this
test hasn't run on Windows before then I wonder about how long
initTestFile will take to create the 4GB file. You've probably
measured already but if you need a speed up then you could change
initTestFile to use a FIleChannel and create the file with the SPARSE
option. Then just position to size-1 and write 1 byte. That should be
faster than writing "e" 4 billion times.
-Alan.
