On 05/12/2018 12:26, Jini George wrote:
Hello!
I needed a clarification regarding the amount of memory unmapped
during imagefile closure in
src/java.base/share/native/libjimage/imageFile.cpp.
I noticed that when the "modules" file is opened in
ImageFileReader::open(), and the contents are mmap()-ed, the size to
be mmap()-ed is derived from map_size().
399 // Memory map image (minimally the index.)
400 _index_data = (u1*)osSupport::map_memory(_fd, _name, 0,
(size_t)map_size());
Which could be _file_size or _index_size, and for 64 bit processes, it
would be _file_size. (about 140 MB)
488 // Retrieve the size of the mapped image.
489 inline u8 map_size() const {
490 return (u8)(memory_map_image ? _file_size : _index_size);
491 }
But when the contents are unmapped in ImageFileReader::close(), the
amount of memory unmapped is only _index_size (which is considerably
lesser than _file_size).
427 // Close image file.
428 void ImageFileReader::close() {
429 // Deallocate the index.
430 if (_index_data) {
431 osSupport::unmap_memory((char*)_index_data, _index_size);
432 _index_data = NULL;
433 }
Wanted to check if this is an oversight, or if there is a reason
behind this and I am missing something. Shouldn't the amount of memory
unmapped be map_size() too ?
It doesn't look right but needs closer examination. However, I'm curious
how you are running into it as it will be completely unmapped when the
VM terminates. Is this a tool or test that runs "in process"?
-Alan
