SO32635860 - Output of sample code (http://stackoverflow.com/q/32635860/2573395)

Explanation and image links.txt

Included in this gist are the two outputs for running the sample code (unmodified except for 
timestamp zero padding) that accompanies the StacKOverflow question "How to prevent flushing 
to disk of a memory map opened on a windows temporary delete-on-close file" 
(http://stackoverflow.com/q/32635860/2573395).

TempFileMapping(false).txt 
-------------------------
Contains the output of running the method with an argument value of 'false'. I.e. closing 
the view before the file handle.

As you can see there is a "blocking delay" (of around 4 seconds) between "handle closing"
and "handle closed", which captures the time it takes for the call to `CloseHandle` on a
chunk file handle to return, for 3 out of the 4 chunks (1, 2, and 0). Only for the last
handle being closed just before the process exits (chunk 3), this delay is not seen. 

Also worth noting is that the delay occurs on the **first** call to close the file handle,
see lines 8, 12 and 39 of the gist.

The accompanying 'TempFileMapping(false).jpg' screen cap (http://i.stack.imgur.com/6gFGD.jpg)
shows that all 4 of the created chunk files are being 'bulk flushed' to disk when they are 
closed.

TempFileMapping(true).txt 
-------------------------
Contains the output of running the method with an argument value of 'true'. I.e. closing 
the file handle before the view.

As you can see there is a "blocking delay" (of around 4 seconds) between "handle closing"
and "handle closed", which captures the time it takes for the call to `CloseHandle` on a
chunk file handle to return, for 2 out of the 4 chunks (1, 2). These are the two chunks
that were being "released" in the sample code. 

Also worth noting is that the delay occurs on the **last** call to close the file handle,
see lines 21 and 26 of the gist.

The accompanying 'TempFileMapping(true).jpg' screen cap (http://i.stack.imgur.com/iCQ9J.png) 
shows that only 2 of the created chunk files are being 'bulk flushed' to disk when they are 
closed, namely the chunks 1 and 2 that were "released" from 'arena 1' while 'arena 2' still 
held an open handle on these files.

Other remarks:
--------------
Note that sufficient memory is available as shown though the 'TempFileMapping.Mem.jpg' screen 
capture (http://i.stack.imgur.com/aqpDn.jpg).

This shows 3 GB of free memory being available before running, suggesting there should be no
need to flush any pages due to memory pressure.

TempFileMapping(false).txt

[00000] Mapping with 2 arenas and unmapping views before closing file handles.
[00000] allocating 100000 pages through arena 1.
[00312] 4 chunks created.
[00327] arena 2 loaded, going to release chunks 1 and 2 from arena 1
[00327] data/page_pool.1.chunk view closing
[00343] data/page_pool.1.chunk view closed
[00343] data/page_pool.1.chunk file handle closing
[04430] data/page_pool.1.chunk file handle closed
[04430] chunk 1 released from arena 1
[04430] data/page_pool.2.chunk view closing
[04477] data/page_pool.2.chunk view closed
[04477] data/page_pool.2.chunk file handle closing
[08595] data/page_pool.2.chunk file handle closed
[08595] chunk 2 released from arena 1
[08611] data/page_pool.0.chunk view closing
[08611] data/page_pool.0.chunk view closed
[08611] data/page_pool.0.chunk file handle closing
[08626] data/page_pool.0.chunk file handle closed
[08626] chunk 0 released from arena 2
[08642] data/page_pool.1.chunk view closing
[08642] data/page_pool.1.chunk view closed
[08642] data/page_pool.1.chunk file handle closing
[08689] data/page_pool.1.chunk file handle closed
[08689] chunk 1 released from arena 2
[08689] data/page_pool.2.chunk view closing
[08689] data/page_pool.2.chunk view closed
[08689] data/page_pool.2.chunk file handle closing
[08720] data/page_pool.2.chunk file handle closed
[08736] chunk 2 released from arena 2
[08736] data/page_pool.3.chunk view closing
[08736] data/page_pool.3.chunk view closed
[08736] data/page_pool.3.chunk file handle closing
[08736] data/page_pool.3.chunk file handle closed
[08736] chunk 3 released from arena 2
[08751] arena 2 destructed
[08751] data/page_pool.0.chunk view closing
[08767] data/page_pool.0.chunk view closed
[08767] data/page_pool.0.chunk file handle closing
[12761] data/page_pool.0.chunk file handle closed
[12761] chunk 0 released from arena 1
[12761] data/page_pool.3.chunk view closing
[12761] data/page_pool.3.chunk view closed
[12776] data/page_pool.3.chunk file handle closing
[12932] data/page_pool.3.chunk file handle closed
[12948] chunk 3 released from arena 1
[12948] arena 1 destructed

TempFileMapping(true).txt

[00000] Mapping with 2 arenas and closing file handles before unmapping views.
[00000] allocating 100000 pages through arena 1.
[00312] 4 chunks created.
[00328] arena 2 loaded, going to release chunks 1 and 2 from arena 1
[00328] data/page_pool.1.chunk file handle closing
[00343] data/page_pool.1.chunk file handle closed
[00343] data/page_pool.1.chunk view closing
[00359] data/page_pool.1.chunk view closed
[00359] chunk 1 released from arena 1
[00359] data/page_pool.2.chunk file handle closing
[00375] data/page_pool.2.chunk file handle closed
[00375] data/page_pool.2.chunk view closing
[00390] data/page_pool.2.chunk view closed
[00406] chunk 2 released from arena 1
[00406] data/page_pool.0.chunk file handle closing
[00406] data/page_pool.0.chunk file handle closed
[00421] data/page_pool.0.chunk view closing
[00421] data/page_pool.0.chunk view closed
[00421] chunk 0 released from arena 2
[00421] data/page_pool.1.chunk file handle closing
[04493] data/page_pool.1.chunk file handle closed
[04493] data/page_pool.1.chunk view closing
[04509] data/page_pool.1.chunk view closed
[04524] chunk 1 released from arena 2
[04524] data/page_pool.2.chunk file handle closing
[09891] data/page_pool.2.chunk file handle closed
[09906] data/page_pool.2.chunk view closing
[09906] data/page_pool.2.chunk view closed
[09922] chunk 2 released from arena 2
[09937] data/page_pool.3.chunk file handle closing
[09937] data/page_pool.3.chunk file handle closed
[09937] data/page_pool.3.chunk view closing
[09953] data/page_pool.3.chunk view closed
[09953] chunk 3 released from arena 2
[09953] arena 2 destructed
[09953] data/page_pool.0.chunk file handle closing
[09969] data/page_pool.0.chunk file handle closed
[09969] data/page_pool.0.chunk view closing
[10000] data/page_pool.0.chunk view closed
[10000] chunk 0 released from arena 1
[10000] data/page_pool.3.chunk file handle closing
[10015] data/page_pool.3.chunk file handle closed
[10015] data/page_pool.3.chunk view closing
[10015] data/page_pool.3.chunk view closed
[10015] chunk 3 released from arena 1
[10015] arena 1 destructed