Hi Dan,
On 2017-11-22 13:53, Daniel D. Daugherty wrote:
On 11/22/17 4:07 AM, Erik Österlund wrote:
Hi,
Some replies...
On 2017-11-21 17:28, Daniel D. Daugherty wrote:
Hi Coleen!
Thanks for making time to review the Thread-SMR stuff again!!
I have added back the other three OpenJDK aliases... This review is
being done on _four_ different OpenJDK aliases.
As always, replies are embedded below...
On 11/20/17 3:12 PM, coleen.phillim...@oracle.com wrote:
http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-09-full/src/hotspot/share/runtime/threadSMR.cpp.html
32 ThreadsList::ThreadsList(int entries) : _length(entries),
_threads(NEW_C_HEAP_ARRAY(JavaThread*, entries + 1, mtGC)),
_next_list(NULL) {
Seems like it should be mtThread rather than mtGC.
Fixed. Definitely an artifact of Erik's original prototype when he
extracted Thread-SMR from his GC work... Thanks for catching it.
Confirmed. At the time I considered the Threads list overheads GC
overheads, but I agree mtThread is a better fit today.
+ return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
Can you add a comment about where this number came from?
I'll have to get that from Erik...
Wow, that looks like code I wrote a *very* long time ago. :) That is
a variation of Knuth's multiplicative hash which is outlined in a
comment in synchronizer.cpp and referred to in that comment as a
phi-based scheme. Basically the magic number is 2^32 * Phi (the
golden ratio), which happens to be a useful value for building a
reasonably simple yet pretty good hash function. It is not the
optimal hash function, but seemed to definitely be good enough for
our purposes.
So a reasonable comment would be:
// The literal value is 2^32 * Phi (the golden ratio).
Yes.
If so, then I'll add it in my wrap up round...
Excellent, thanks Dan.
/Erik
Dan
Thanks,
/Erik
