On 09/08/2015 12:37 PM, David M. Lloyd wrote: > On 09/08/2015 04:30 AM, Andrew Haley wrote: >> On 09/08/2015 09:58 AM, Paul Sandoz wrote: > >> However, I think that some cleverness in HotSpot could make that cost >> go away. For example, we could associate with every >> MappedByteBufferForwardingObject a protection page in memory. When >> the forwarding object is unmapped that page is write-protected. Every >> access to the mapped file is preceded by a write to the page; there >> don't have to be any memory fence instructions. The protection page >> would stay until the forwarding object was unmapped.
Sorry, I meant "until the forwarding object was collected". > If you're already doing this, why not skip the level of indirection and > mprotect the entire mapped region to PROT_NONE when the user unmaps? Because one page has to hang around until the forwarding object is garbage collected. The entire mapping doesn't. Andrew.
