459042 - -memstats (GCStats) other fields can overflow and return large number

Status: VERIFIED FIXED

(Tamarin Graveyard :: Garbage Collection (mmGC), defect, P3)

Description

[Dan Schaffer]

Is this caused by other being a negative number?  Certain tests will show other bytes are being e.g. 3986.4MB

To reproduce
- Enable GCStats=1 in mm.cfg
Run http://asteam/memoryperf/papervision/dof05.swf 
view flashlog.txt searching for 409 or looking for a case where mmgc > private
See the “other” memory at 4095M (~ 4 gb) is erroneous, mmgc should not be > private,
 [mem] ------- gross stats -----
[mem] private 17113 (66.8M) 100%
[mem]     mmgc 17248 (67.4M) 100%
[mem]         unmanaged 14560 (56.9M) 85%
[mem]         managed 1292 (5.0M) 7%
[mem]         free 1321 (5.2M) 7%
[mem]     jit 0 (0K) 0%
[mem]     other 1048441 (4095.5M) 6126%
[mem] bytes (interal fragmentation) 15723 (61.4M) 99%
[mem]     managed bytes  1187 (4.6M) 91%
[mem]     unmanaged bytes  14536 (56.8M) 99%
[mem] -------- gross stats end -----

Comment 1

[Trevor Baker]

Open to Erik

Comment 2

[Tommy Reilly]

untouched pages returned by GCHeap won't count in private bytes.  GCHeap should touch every page it returns, there's actually a decent rationale for this which is that you don't want the program to crash later accessing the memory it allocated if real memory is exhausted.  With that in place this problem should go away or more investigation is necessary if that's not it.

Comment 3

[Erik Tierney]

Attachment: Use vm_protect instead of mprotect

Switch mac builds to call vm_protect with set_maximum=true instead of just mprotect.  mprotect was causing the pages to be marked as shared memory, vm_protect does not do that when set_maximum is true.  This was causing private bytes to be under reported as lots of private pages were ending up as shared pages.

Comment 4

[Erik Tierney]

Attachment: Patch with debugging statement removed

Comment 5

[Erik Tierney]

Attachment: Try again with new file name.

Comment 6

[Erik Tierney]

Attachment: patch that works with redux

Comment 7

[Erik Tierney]

Pushed:  http://hg.mozilla.org/tamarin-redux/rev/aa8f4ef5466e