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7098085: G1: partially-young GCs not initiated under certain circumstances

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Reviewed-by: ysr, brutisso
This commit is contained in:
Antonios Printezis 2011-10-13 13:54:29 -04:00
parent 4738ed88a5
commit d1c6787aa1
1 changed files with 42 additions and 12 deletions
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54
hotspot/src/share/vm/gc_implementation/g1/concurrentMarkThread.cpp
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@ -215,19 +215,19 @@ void ConcurrentMarkThread::run() {
gclog_or_tty->print_cr("[GC concurrent-cleanup-start]");
}
// Now do the remainder of the cleanup operation.
// Now do the concurrent cleanup operation.
_cm->completeCleanup();
// Notify anyone who's waiting that there are no more free
// regions coming. We have to do this before we join the STS,
// otherwise we might deadlock: a GC worker could be blocked
// waiting for the notification whereas this thread will be
// blocked for the pause to finish while it's trying to join
// the STS, which is conditional on the GC workers finishing.
g1h->reset_free_regions_coming();
_sts.join();
g1_policy->record_concurrent_mark_cleanup_completed();
_sts.leave();
// Notify anyone who's waiting that there are no more free
// regions coming. We have to do this before we join the STS
// (in fact, we should not attempt to join the STS in the
// interval between finishing the cleanup pause and clearing
// the free_regions_coming flag) otherwise we might deadlock:
// a GC worker could be blocked waiting for the notification
// whereas this thread will be blocked for the pause to finish
// while it's trying to join the STS, which is conditional on
// the GC workers finishing.
g1h->reset_free_regions_coming();
double cleanup_end_sec = os::elapsedTime();
if (PrintGC) {
@ -240,6 +240,36 @@ void ConcurrentMarkThread::run() {
guarantee(cm()->cleanup_list_is_empty(),
"at this point there should be no regions on the cleanup list");
// There is a tricky race before recording that the concurrent
// cleanup has completed and a potential Full GC starting around
// the same time. We want to make sure that the Full GC calls
// abort() on concurrent mark after
// record_concurrent_mark_cleanup_completed(), since abort() is
// the method that will reset the concurrent mark state. If we
// end up calling record_concurrent_mark_cleanup_completed()
// after abort() then we might incorrectly undo some of the work
// abort() did. Checking the has_aborted() flag after joining
// the STS allows the correct ordering of the two methods. There
// are two scenarios:
//
// a) If we reach here before the Full GC, the fact that we have
// joined the STS means that the Full GC cannot start until we
// leave the STS, so record_concurrent_mark_cleanup_completed()
// will complete before abort() is called.
//
// b) If we reach here during the Full GC, we'll be held up from
// joining the STS until the Full GC is done, which means that
// abort() will have completed and has_aborted() will return
// true to prevent us from calling
// record_concurrent_mark_cleanup_completed() (and, in fact, it's
// not needed any more as the concurrent mark state has been
// already reset).
_sts.join();
if (!cm()->has_aborted()) {
g1_policy->record_concurrent_mark_cleanup_completed();
}
_sts.leave();
if (cm()->has_aborted()) {
if (PrintGC) {
gclog_or_tty->date_stamp(PrintGCDateStamps);
@ -248,7 +278,7 @@ void ConcurrentMarkThread::run() {
}
}
// we now want to allow clearing of the marking bitmap to be
// We now want to allow clearing of the marking bitmap to be
// suspended by a collection pause.
_sts.join();
_cm->clearNextBitmap();