1.1 --- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Tue Mar 29 22:36:16 2011 -0400
1.2 +++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Wed Mar 30 10:26:59 2011 -0400
1.3 @@ -28,6 +28,7 @@
1.4 #include "gc_implementation/g1/concurrentG1Refine.hpp"
1.5 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
1.6 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
1.7 +#include "gc_implementation/g1/g1AllocRegion.inline.hpp"
1.8 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
1.9 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
1.10 #include "gc_implementation/g1/g1MarkSweep.hpp"
1.11 @@ -517,8 +518,7 @@
1.12 return NULL;
1.13 }
1.14
1.15 -HeapRegion* G1CollectedHeap::new_region_work(size_t word_size,
1.16 - bool do_expand) {
1.17 +HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
1.18 assert(!isHumongous(word_size) ||
1.19 word_size <= (size_t) HeapRegion::GrainWords,
1.20 "the only time we use this to allocate a humongous region is "
1.21 @@ -566,7 +566,7 @@
1.22 size_t word_size) {
1.23 HeapRegion* alloc_region = NULL;
1.24 if (_gc_alloc_region_counts[purpose] < g1_policy()->max_regions(purpose)) {
1.25 - alloc_region = new_region_work(word_size, true /* do_expand */);
1.26 + alloc_region = new_region(word_size, true /* do_expand */);
1.27 if (purpose == GCAllocForSurvived && alloc_region != NULL) {
1.28 alloc_region->set_survivor();
1.29 }
1.30 @@ -587,7 +587,7 @@
1.31 // Only one region to allocate, no need to go through the slower
1.32 // path. The caller will attempt the expasion if this fails, so
1.33 // let's not try to expand here too.
1.34 - HeapRegion* hr = new_region_work(word_size, false /* do_expand */);
1.35 + HeapRegion* hr = new_region(word_size, false /* do_expand */);
1.36 if (hr != NULL) {
1.37 first = hr->hrs_index();
1.38 } else {
1.39 @@ -788,407 +788,12 @@
1.40 return result;
1.41 }
1.42
1.43 -void
1.44 -G1CollectedHeap::retire_cur_alloc_region(HeapRegion* cur_alloc_region) {
1.45 - // Other threads might still be trying to allocate using CASes out
1.46 - // of the region we are retiring, as they can do so without holding
1.47 - // the Heap_lock. So we first have to make sure that noone else can
1.48 - // allocate in it by doing a maximal allocation. Even if our CAS
1.49 - // attempt fails a few times, we'll succeed sooner or later given
1.50 - // that a failed CAS attempt mean that the region is getting closed
1.51 - // to being full (someone else succeeded in allocating into it).
1.52 - size_t free_word_size = cur_alloc_region->free() / HeapWordSize;
1.53 -
1.54 - // This is the minimum free chunk we can turn into a dummy
1.55 - // object. If the free space falls below this, then noone can
1.56 - // allocate in this region anyway (all allocation requests will be
1.57 - // of a size larger than this) so we won't have to perform the dummy
1.58 - // allocation.
1.59 - size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
1.60 -
1.61 - while (free_word_size >= min_word_size_to_fill) {
1.62 - HeapWord* dummy =
1.63 - cur_alloc_region->par_allocate_no_bot_updates(free_word_size);
1.64 - if (dummy != NULL) {
1.65 - // If the allocation was successful we should fill in the space.
1.66 - CollectedHeap::fill_with_object(dummy, free_word_size);
1.67 - break;
1.68 - }
1.69 -
1.70 - free_word_size = cur_alloc_region->free() / HeapWordSize;
1.71 - // It's also possible that someone else beats us to the
1.72 - // allocation and they fill up the region. In that case, we can
1.73 - // just get out of the loop
1.74 - }
1.75 - assert(cur_alloc_region->free() / HeapWordSize < min_word_size_to_fill,
1.76 - "sanity");
1.77 -
1.78 - retire_cur_alloc_region_common(cur_alloc_region);
1.79 - assert(_cur_alloc_region == NULL, "post-condition");
1.80 -}
1.81 -
1.82 -// See the comment in the .hpp file about the locking protocol and
1.83 -// assumptions of this method (and other related ones).
1.84 -HeapWord*
1.85 -G1CollectedHeap::replace_cur_alloc_region_and_allocate(size_t word_size,
1.86 - bool at_safepoint,
1.87 - bool do_dirtying,
1.88 - bool can_expand) {
1.89 - assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1.90 - assert(_cur_alloc_region == NULL,
1.91 - "replace_cur_alloc_region_and_allocate() should only be called "
1.92 - "after retiring the previous current alloc region");
1.93 - assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
1.94 - "at_safepoint and is_at_safepoint() should be a tautology");
1.95 - assert(!can_expand || g1_policy()->can_expand_young_list(),
1.96 - "we should not call this method with can_expand == true if "
1.97 - "we are not allowed to expand the young gen");
1.98 -
1.99 - if (can_expand || !g1_policy()->is_young_list_full()) {
1.100 - HeapRegion* new_cur_alloc_region = new_alloc_region(word_size);
1.101 - if (new_cur_alloc_region != NULL) {
1.102 - assert(new_cur_alloc_region->is_empty(),
1.103 - "the newly-allocated region should be empty, "
1.104 - "as right now we only allocate new regions out of the free list");
1.105 - g1_policy()->update_region_num(true /* next_is_young */);
1.106 - set_region_short_lived_locked(new_cur_alloc_region);
1.107 -
1.108 - assert(!new_cur_alloc_region->isHumongous(),
1.109 - "Catch a regression of this bug.");
1.110 -
1.111 - // We need to ensure that the stores to _cur_alloc_region and,
1.112 - // subsequently, to top do not float above the setting of the
1.113 - // young type.
1.114 - OrderAccess::storestore();
1.115 -
1.116 - // Now, perform the allocation out of the region we just
1.117 - // allocated. Note that noone else can access that region at
1.118 - // this point (as _cur_alloc_region has not been updated yet),
1.119 - // so we can just go ahead and do the allocation without any
1.120 - // atomics (and we expect this allocation attempt to
1.121 - // suceeded). Given that other threads can attempt an allocation
1.122 - // with a CAS and without needing the Heap_lock, if we assigned
1.123 - // the new region to _cur_alloc_region before first allocating
1.124 - // into it other threads might have filled up the new region
1.125 - // before we got a chance to do the allocation ourselves. In
1.126 - // that case, we would have needed to retire the region, grab a
1.127 - // new one, and go through all this again. Allocating out of the
1.128 - // new region before assigning it to _cur_alloc_region avoids
1.129 - // all this.
1.130 - HeapWord* result =
1.131 - new_cur_alloc_region->allocate_no_bot_updates(word_size);
1.132 - assert(result != NULL, "we just allocate out of an empty region "
1.133 - "so allocation should have been successful");
1.134 - assert(is_in(result), "result should be in the heap");
1.135 -
1.136 - // Now make sure that the store to _cur_alloc_region does not
1.137 - // float above the store to top.
1.138 - OrderAccess::storestore();
1.139 - _cur_alloc_region = new_cur_alloc_region;
1.140 -
1.141 - if (!at_safepoint) {
1.142 - Heap_lock->unlock();
1.143 - }
1.144 -
1.145 - // do the dirtying, if necessary, after we release the Heap_lock
1.146 - if (do_dirtying) {
1.147 - dirty_young_block(result, word_size);
1.148 - }
1.149 - return result;
1.150 - }
1.151 - }
1.152 -
1.153 - assert(_cur_alloc_region == NULL, "we failed to allocate a new current "
1.154 - "alloc region, it should still be NULL");
1.155 - assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1.156 - return NULL;
1.157 -}
1.158 -
1.159 -// See the comment in the .hpp file about the locking protocol and
1.160 -// assumptions of this method (and other related ones).
1.161 -HeapWord*
1.162 -G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
1.163 - assert_heap_locked_and_not_at_safepoint();
1.164 - assert(!isHumongous(word_size), "attempt_allocation_slow() should not be "
1.165 - "used for humongous allocations");
1.166 -
1.167 - // We should only reach here when we were unable to allocate
1.168 - // otherwise. So, we should have not active current alloc region.
1.169 - assert(_cur_alloc_region == NULL, "current alloc region should be NULL");
1.170 -
1.171 - // We will loop while succeeded is false, which means that we tried
1.172 - // to do a collection, but the VM op did not succeed. So, when we
1.173 - // exit the loop, either one of the allocation attempts was
1.174 - // successful, or we succeeded in doing the VM op but which was
1.175 - // unable to allocate after the collection.
1.176 - for (int try_count = 1; /* we'll return or break */; try_count += 1) {
1.177 - bool succeeded = true;
1.178 -
1.179 - // Every time we go round the loop we should be holding the Heap_lock.
1.180 - assert_heap_locked();
1.181 -
1.182 - if (GC_locker::is_active_and_needs_gc()) {
1.183 - // We are locked out of GC because of the GC locker. We can
1.184 - // allocate a new region only if we can expand the young gen.
1.185 -
1.186 - if (g1_policy()->can_expand_young_list()) {
1.187 - // Yes, we are allowed to expand the young gen. Let's try to
1.188 - // allocate a new current alloc region.
1.189 - HeapWord* result =
1.190 - replace_cur_alloc_region_and_allocate(word_size,
1.191 - false, /* at_safepoint */
1.192 - true, /* do_dirtying */
1.193 - true /* can_expand */);
1.194 - if (result != NULL) {
1.195 - assert_heap_not_locked();
1.196 - return result;
1.197 - }
1.198 - }
1.199 - // We could not expand the young gen further (or we could but we
1.200 - // failed to allocate a new region). We'll stall until the GC
1.201 - // locker forces a GC.
1.202 -
1.203 - // If this thread is not in a jni critical section, we stall
1.204 - // the requestor until the critical section has cleared and
1.205 - // GC allowed. When the critical section clears, a GC is
1.206 - // initiated by the last thread exiting the critical section; so
1.207 - // we retry the allocation sequence from the beginning of the loop,
1.208 - // rather than causing more, now probably unnecessary, GC attempts.
1.209 - JavaThread* jthr = JavaThread::current();
1.210 - assert(jthr != NULL, "sanity");
1.211 - if (jthr->in_critical()) {
1.212 - if (CheckJNICalls) {
1.213 - fatal("Possible deadlock due to allocating while"
1.214 - " in jni critical section");
1.215 - }
1.216 - // We are returning NULL so the protocol is that we're still
1.217 - // holding the Heap_lock.
1.218 - assert_heap_locked();
1.219 - return NULL;
1.220 - }
1.221 -
1.222 - Heap_lock->unlock();
1.223 - GC_locker::stall_until_clear();
1.224 -
1.225 - // No need to relock the Heap_lock. We'll fall off to the code
1.226 - // below the else-statement which assumes that we are not
1.227 - // holding the Heap_lock.
1.228 - } else {
1.229 - // We are not locked out. So, let's try to do a GC. The VM op
1.230 - // will retry the allocation before it completes.
1.231 -
1.232 - // Read the GC count while holding the Heap_lock
1.233 - unsigned int gc_count_before = SharedHeap::heap()->total_collections();
1.234 -
1.235 - Heap_lock->unlock();
1.236 -
1.237 - HeapWord* result =
1.238 - do_collection_pause(word_size, gc_count_before, &succeeded);
1.239 - assert_heap_not_locked();
1.240 - if (result != NULL) {
1.241 - assert(succeeded, "the VM op should have succeeded");
1.242 -
1.243 - // Allocations that take place on VM operations do not do any
1.244 - // card dirtying and we have to do it here.
1.245 - dirty_young_block(result, word_size);
1.246 - return result;
1.247 - }
1.248 - }
1.249 -
1.250 - // Both paths that get us here from above unlock the Heap_lock.
1.251 - assert_heap_not_locked();
1.252 -
1.253 - // We can reach here when we were unsuccessful in doing a GC,
1.254 - // because another thread beat us to it, or because we were locked
1.255 - // out of GC due to the GC locker. In either case a new alloc
1.256 - // region might be available so we will retry the allocation.
1.257 - HeapWord* result = attempt_allocation(word_size);
1.258 - if (result != NULL) {
1.259 - assert_heap_not_locked();
1.260 - return result;
1.261 - }
1.262 -
1.263 - // So far our attempts to allocate failed. The only time we'll go
1.264 - // around the loop and try again is if we tried to do a GC and the
1.265 - // VM op that we tried to schedule was not successful because
1.266 - // another thread beat us to it. If that happened it's possible
1.267 - // that by the time we grabbed the Heap_lock again and tried to
1.268 - // allocate other threads filled up the young generation, which
1.269 - // means that the allocation attempt after the GC also failed. So,
1.270 - // it's worth trying to schedule another GC pause.
1.271 - if (succeeded) {
1.272 - break;
1.273 - }
1.274 -
1.275 - // Give a warning if we seem to be looping forever.
1.276 - if ((QueuedAllocationWarningCount > 0) &&
1.277 - (try_count % QueuedAllocationWarningCount == 0)) {
1.278 - warning("G1CollectedHeap::attempt_allocation_slow() "
1.279 - "retries %d times", try_count);
1.280 - }
1.281 - }
1.282 -
1.283 - assert_heap_locked();
1.284 - return NULL;
1.285 -}
1.286 -
1.287 -// See the comment in the .hpp file about the locking protocol and
1.288 -// assumptions of this method (and other related ones).
1.289 -HeapWord*
1.290 -G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1.291 - bool at_safepoint) {
1.292 - // This is the method that will allocate a humongous object. All
1.293 - // allocation paths that attempt to allocate a humongous object
1.294 - // should eventually reach here. Currently, the only paths are from
1.295 - // mem_allocate() and attempt_allocation_at_safepoint().
1.296 - assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1.297 - assert(isHumongous(word_size), "attempt_allocation_humongous() "
1.298 - "should only be used for humongous allocations");
1.299 - assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
1.300 - "at_safepoint and is_at_safepoint() should be a tautology");
1.301 -
1.302 - HeapWord* result = NULL;
1.303 -
1.304 - // We will loop while succeeded is false, which means that we tried
1.305 - // to do a collection, but the VM op did not succeed. So, when we
1.306 - // exit the loop, either one of the allocation attempts was
1.307 - // successful, or we succeeded in doing the VM op but which was
1.308 - // unable to allocate after the collection.
1.309 - for (int try_count = 1; /* we'll return or break */; try_count += 1) {
1.310 - bool succeeded = true;
1.311 -
1.312 - // Given that humongous objects are not allocated in young
1.313 - // regions, we'll first try to do the allocation without doing a
1.314 - // collection hoping that there's enough space in the heap.
1.315 - result = humongous_obj_allocate(word_size);
1.316 - assert(_cur_alloc_region == NULL || !_cur_alloc_region->isHumongous(),
1.317 - "catch a regression of this bug.");
1.318 - if (result != NULL) {
1.319 - if (!at_safepoint) {
1.320 - // If we're not at a safepoint, unlock the Heap_lock.
1.321 - Heap_lock->unlock();
1.322 - }
1.323 - return result;
1.324 - }
1.325 -
1.326 - // If we failed to allocate the humongous object, we should try to
1.327 - // do a collection pause (if we're allowed) in case it reclaims
1.328 - // enough space for the allocation to succeed after the pause.
1.329 - if (!at_safepoint) {
1.330 - // Read the GC count while holding the Heap_lock
1.331 - unsigned int gc_count_before = SharedHeap::heap()->total_collections();
1.332 -
1.333 - // If we're allowed to do a collection we're not at a
1.334 - // safepoint, so it is safe to unlock the Heap_lock.
1.335 - Heap_lock->unlock();
1.336 -
1.337 - result = do_collection_pause(word_size, gc_count_before, &succeeded);
1.338 - assert_heap_not_locked();
1.339 - if (result != NULL) {
1.340 - assert(succeeded, "the VM op should have succeeded");
1.341 - return result;
1.342 - }
1.343 -
1.344 - // If we get here, the VM operation either did not succeed
1.345 - // (i.e., another thread beat us to it) or it succeeded but
1.346 - // failed to allocate the object.
1.347 -
1.348 - // If we're allowed to do a collection we're not at a
1.349 - // safepoint, so it is safe to lock the Heap_lock.
1.350 - Heap_lock->lock();
1.351 - }
1.352 -
1.353 - assert(result == NULL, "otherwise we should have exited the loop earlier");
1.354 -
1.355 - // So far our attempts to allocate failed. The only time we'll go
1.356 - // around the loop and try again is if we tried to do a GC and the
1.357 - // VM op that we tried to schedule was not successful because
1.358 - // another thread beat us to it. That way it's possible that some
1.359 - // space was freed up by the thread that successfully scheduled a
1.360 - // GC. So it's worth trying to allocate again.
1.361 - if (succeeded) {
1.362 - break;
1.363 - }
1.364 -
1.365 - // Give a warning if we seem to be looping forever.
1.366 - if ((QueuedAllocationWarningCount > 0) &&
1.367 - (try_count % QueuedAllocationWarningCount == 0)) {
1.368 - warning("G1CollectedHeap::attempt_allocation_humongous "
1.369 - "retries %d times", try_count);
1.370 - }
1.371 - }
1.372 -
1.373 - assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1.374 - return NULL;
1.375 -}
1.376 -
1.377 -HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1.378 - bool expect_null_cur_alloc_region) {
1.379 - assert_at_safepoint(true /* should_be_vm_thread */);
1.380 - assert(_cur_alloc_region == NULL || !expect_null_cur_alloc_region,
1.381 - err_msg("the current alloc region was unexpectedly found "
1.382 - "to be non-NULL, cur alloc region: "PTR_FORMAT" "
1.383 - "expect_null_cur_alloc_region: %d word_size: "SIZE_FORMAT,
1.384 - _cur_alloc_region, expect_null_cur_alloc_region, word_size));
1.385 -
1.386 - if (!isHumongous(word_size)) {
1.387 - if (!expect_null_cur_alloc_region) {
1.388 - HeapRegion* cur_alloc_region = _cur_alloc_region;
1.389 - if (cur_alloc_region != NULL) {
1.390 - // We are at a safepoint so no reason to use the MT-safe version.
1.391 - HeapWord* result = cur_alloc_region->allocate_no_bot_updates(word_size);
1.392 - if (result != NULL) {
1.393 - assert(is_in(result), "result should be in the heap");
1.394 -
1.395 - // We will not do any dirtying here. This is guaranteed to be
1.396 - // called during a safepoint and the thread that scheduled the
1.397 - // pause will do the dirtying if we return a non-NULL result.
1.398 - return result;
1.399 - }
1.400 -
1.401 - retire_cur_alloc_region_common(cur_alloc_region);
1.402 - }
1.403 - }
1.404 -
1.405 - assert(_cur_alloc_region == NULL,
1.406 - "at this point we should have no cur alloc region");
1.407 - return replace_cur_alloc_region_and_allocate(word_size,
1.408 - true, /* at_safepoint */
1.409 - false /* do_dirtying */,
1.410 - false /* can_expand */);
1.411 - } else {
1.412 - return attempt_allocation_humongous(word_size,
1.413 - true /* at_safepoint */);
1.414 - }
1.415 -
1.416 - ShouldNotReachHere();
1.417 -}
1.418 -
1.419 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
1.420 assert_heap_not_locked_and_not_at_safepoint();
1.421 - assert(!isHumongous(word_size), "we do not allow TLABs of humongous size");
1.422 -
1.423 - // First attempt: Try allocating out of the current alloc region
1.424 - // using a CAS. If that fails, take the Heap_lock and retry the
1.425 - // allocation, potentially replacing the current alloc region.
1.426 - HeapWord* result = attempt_allocation(word_size);
1.427 - if (result != NULL) {
1.428 - assert_heap_not_locked();
1.429 - return result;
1.430 - }
1.431 -
1.432 - // Second attempt: Go to the slower path where we might try to
1.433 - // schedule a collection.
1.434 - result = attempt_allocation_slow(word_size);
1.435 - if (result != NULL) {
1.436 - assert_heap_not_locked();
1.437 - return result;
1.438 - }
1.439 -
1.440 - assert_heap_locked();
1.441 - // Need to unlock the Heap_lock before returning.
1.442 - Heap_lock->unlock();
1.443 - return NULL;
1.444 + assert(!isHumongous(word_size), "we do not allow humongous TLABs");
1.445 +
1.446 + unsigned int dummy_gc_count_before;
1.447 + return attempt_allocation(word_size, &dummy_gc_count_before);
1.448 }
1.449
1.450 HeapWord*
1.451 @@ -1200,48 +805,18 @@
1.452 assert(!is_tlab, "mem_allocate() this should not be called directly "
1.453 "to allocate TLABs");
1.454
1.455 - // Loop until the allocation is satisified,
1.456 - // or unsatisfied after GC.
1.457 + // Loop until the allocation is satisified, or unsatisfied after GC.
1.458 for (int try_count = 1; /* we'll return */; try_count += 1) {
1.459 unsigned int gc_count_before;
1.460 - {
1.461 - if (!isHumongous(word_size)) {
1.462 - // First attempt: Try allocating out of the current alloc region
1.463 - // using a CAS. If that fails, take the Heap_lock and retry the
1.464 - // allocation, potentially replacing the current alloc region.
1.465 - HeapWord* result = attempt_allocation(word_size);
1.466 - if (result != NULL) {
1.467 - assert_heap_not_locked();
1.468 - return result;
1.469 - }
1.470 -
1.471 - assert_heap_locked();
1.472 -
1.473 - // Second attempt: Go to the slower path where we might try to
1.474 - // schedule a collection.
1.475 - result = attempt_allocation_slow(word_size);
1.476 - if (result != NULL) {
1.477 - assert_heap_not_locked();
1.478 - return result;
1.479 - }
1.480 - } else {
1.481 - // attempt_allocation_humongous() requires the Heap_lock to be held.
1.482 - Heap_lock->lock();
1.483 -
1.484 - HeapWord* result = attempt_allocation_humongous(word_size,
1.485 - false /* at_safepoint */);
1.486 - if (result != NULL) {
1.487 - assert_heap_not_locked();
1.488 - return result;
1.489 - }
1.490 - }
1.491 -
1.492 - assert_heap_locked();
1.493 - // Read the gc count while the heap lock is held.
1.494 - gc_count_before = SharedHeap::heap()->total_collections();
1.495 -
1.496 - // Release the Heap_lock before attempting the collection.
1.497 - Heap_lock->unlock();
1.498 +
1.499 + HeapWord* result = NULL;
1.500 + if (!isHumongous(word_size)) {
1.501 + result = attempt_allocation(word_size, &gc_count_before);
1.502 + } else {
1.503 + result = attempt_allocation_humongous(word_size, &gc_count_before);
1.504 + }
1.505 + if (result != NULL) {
1.506 + return result;
1.507 }
1.508
1.509 // Create the garbage collection operation...
1.510 @@ -1249,7 +824,6 @@
1.511 // ...and get the VM thread to execute it.
1.512 VMThread::execute(&op);
1.513
1.514 - assert_heap_not_locked();
1.515 if (op.prologue_succeeded() && op.pause_succeeded()) {
1.516 // If the operation was successful we'll return the result even
1.517 // if it is NULL. If the allocation attempt failed immediately
1.518 @@ -1275,21 +849,207 @@
1.519 }
1.520
1.521 ShouldNotReachHere();
1.522 + return NULL;
1.523 }
1.524
1.525 -void G1CollectedHeap::abandon_cur_alloc_region() {
1.526 +HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
1.527 + unsigned int *gc_count_before_ret) {
1.528 + // Make sure you read the note in attempt_allocation_humongous().
1.529 +
1.530 + assert_heap_not_locked_and_not_at_safepoint();
1.531 + assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
1.532 + "be called for humongous allocation requests");
1.533 +
1.534 + // We should only get here after the first-level allocation attempt
1.535 + // (attempt_allocation()) failed to allocate.
1.536 +
1.537 + // We will loop until a) we manage to successfully perform the
1.538 + // allocation or b) we successfully schedule a collection which
1.539 + // fails to perform the allocation. b) is the only case when we'll
1.540 + // return NULL.
1.541 + HeapWord* result = NULL;
1.542 + for (int try_count = 1; /* we'll return */; try_count += 1) {
1.543 + bool should_try_gc;
1.544 + unsigned int gc_count_before;
1.545 +
1.546 + {
1.547 + MutexLockerEx x(Heap_lock);
1.548 +
1.549 + result = _mutator_alloc_region.attempt_allocation_locked(word_size,
1.550 + false /* bot_updates */);
1.551 + if (result != NULL) {
1.552 + return result;
1.553 + }
1.554 +
1.555 + // If we reach here, attempt_allocation_locked() above failed to
1.556 + // allocate a new region. So the mutator alloc region should be NULL.
1.557 + assert(_mutator_alloc_region.get() == NULL, "only way to get here");
1.558 +
1.559 + if (GC_locker::is_active_and_needs_gc()) {
1.560 + if (g1_policy()->can_expand_young_list()) {
1.561 + result = _mutator_alloc_region.attempt_allocation_force(word_size,
1.562 + false /* bot_updates */);
1.563 + if (result != NULL) {
1.564 + return result;
1.565 + }
1.566 + }
1.567 + should_try_gc = false;
1.568 + } else {
1.569 + // Read the GC count while still holding the Heap_lock.
1.570 + gc_count_before = SharedHeap::heap()->total_collections();
1.571 + should_try_gc = true;
1.572 + }
1.573 + }
1.574 +
1.575 + if (should_try_gc) {
1.576 + bool succeeded;
1.577 + result = do_collection_pause(word_size, gc_count_before, &succeeded);
1.578 + if (result != NULL) {
1.579 + assert(succeeded, "only way to get back a non-NULL result");
1.580 + return result;
1.581 + }
1.582 +
1.583 + if (succeeded) {
1.584 + // If we get here we successfully scheduled a collection which
1.585 + // failed to allocate. No point in trying to allocate
1.586 + // further. We'll just return NULL.
1.587 + MutexLockerEx x(Heap_lock);
1.588 + *gc_count_before_ret = SharedHeap::heap()->total_collections();
1.589 + return NULL;
1.590 + }
1.591 + } else {
1.592 + GC_locker::stall_until_clear();
1.593 + }
1.594 +
1.595 + // We can reach here if we were unsuccessul in scheduling a
1.596 + // collection (because another thread beat us to it) or if we were
1.597 + // stalled due to the GC locker. In either can we should retry the
1.598 + // allocation attempt in case another thread successfully
1.599 + // performed a collection and reclaimed enough space. We do the
1.600 + // first attempt (without holding the Heap_lock) here and the
1.601 + // follow-on attempt will be at the start of the next loop
1.602 + // iteration (after taking the Heap_lock).
1.603 + result = _mutator_alloc_region.attempt_allocation(word_size,
1.604 + false /* bot_updates */);
1.605 + if (result != NULL ){
1.606 + return result;
1.607 + }
1.608 +
1.609 + // Give a warning if we seem to be looping forever.
1.610 + if ((QueuedAllocationWarningCount > 0) &&
1.611 + (try_count % QueuedAllocationWarningCount == 0)) {
1.612 + warning("G1CollectedHeap::attempt_allocation_slow() "
1.613 + "retries %d times", try_count);
1.614 + }
1.615 + }
1.616 +
1.617 + ShouldNotReachHere();
1.618 + return NULL;
1.619 +}
1.620 +
1.621 +HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1.622 + unsigned int * gc_count_before_ret) {
1.623 + // The structure of this method has a lot of similarities to
1.624 + // attempt_allocation_slow(). The reason these two were not merged
1.625 + // into a single one is that such a method would require several "if
1.626 + // allocation is not humongous do this, otherwise do that"
1.627 + // conditional paths which would obscure its flow. In fact, an early
1.628 + // version of this code did use a unified method which was harder to
1.629 + // follow and, as a result, it had subtle bugs that were hard to
1.630 + // track down. So keeping these two methods separate allows each to
1.631 + // be more readable. It will be good to keep these two in sync as
1.632 + // much as possible.
1.633 +
1.634 + assert_heap_not_locked_and_not_at_safepoint();
1.635 + assert(isHumongous(word_size), "attempt_allocation_humongous() "
1.636 + "should only be called for humongous allocations");
1.637 +
1.638 + // We will loop until a) we manage to successfully perform the
1.639 + // allocation or b) we successfully schedule a collection which
1.640 + // fails to perform the allocation. b) is the only case when we'll
1.641 + // return NULL.
1.642 + HeapWord* result = NULL;
1.643 + for (int try_count = 1; /* we'll return */; try_count += 1) {
1.644 + bool should_try_gc;
1.645 + unsigned int gc_count_before;
1.646 +
1.647 + {
1.648 + MutexLockerEx x(Heap_lock);
1.649 +
1.650 + // Given that humongous objects are not allocated in young
1.651 + // regions, we'll first try to do the allocation without doing a
1.652 + // collection hoping that there's enough space in the heap.
1.653 + result = humongous_obj_allocate(word_size);
1.654 + if (result != NULL) {
1.655 + return result;
1.656 + }
1.657 +
1.658 + if (GC_locker::is_active_and_needs_gc()) {
1.659 + should_try_gc = false;
1.660 + } else {
1.661 + // Read the GC count while still holding the Heap_lock.
1.662 + gc_count_before = SharedHeap::heap()->total_collections();
1.663 + should_try_gc = true;
1.664 + }
1.665 + }
1.666 +
1.667 + if (should_try_gc) {
1.668 + // If we failed to allocate the humongous object, we should try to
1.669 + // do a collection pause (if we're allowed) in case it reclaims
1.670 + // enough space for the allocation to succeed after the pause.
1.671 +
1.672 + bool succeeded;
1.673 + result = do_collection_pause(word_size, gc_count_before, &succeeded);
1.674 + if (result != NULL) {
1.675 + assert(succeeded, "only way to get back a non-NULL result");
1.676 + return result;
1.677 + }
1.678 +
1.679 + if (succeeded) {
1.680 + // If we get here we successfully scheduled a collection which
1.681 + // failed to allocate. No point in trying to allocate
1.682 + // further. We'll just return NULL.
1.683 + MutexLockerEx x(Heap_lock);
1.684 + *gc_count_before_ret = SharedHeap::heap()->total_collections();
1.685 + return NULL;
1.686 + }
1.687 + } else {
1.688 + GC_locker::stall_until_clear();
1.689 + }
1.690 +
1.691 + // We can reach here if we were unsuccessul in scheduling a
1.692 + // collection (because another thread beat us to it) or if we were
1.693 + // stalled due to the GC locker. In either can we should retry the
1.694 + // allocation attempt in case another thread successfully
1.695 + // performed a collection and reclaimed enough space. Give a
1.696 + // warning if we seem to be looping forever.
1.697 +
1.698 + if ((QueuedAllocationWarningCount > 0) &&
1.699 + (try_count % QueuedAllocationWarningCount == 0)) {
1.700 + warning("G1CollectedHeap::attempt_allocation_humongous() "
1.701 + "retries %d times", try_count);
1.702 + }
1.703 + }
1.704 +
1.705 + ShouldNotReachHere();
1.706 + return NULL;
1.707 +}
1.708 +
1.709 +HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1.710 + bool expect_null_mutator_alloc_region) {
1.711 assert_at_safepoint(true /* should_be_vm_thread */);
1.712 -
1.713 - HeapRegion* cur_alloc_region = _cur_alloc_region;
1.714 - if (cur_alloc_region != NULL) {
1.715 - assert(!cur_alloc_region->is_empty(),
1.716 - "the current alloc region can never be empty");
1.717 - assert(cur_alloc_region->is_young(),
1.718 - "the current alloc region should be young");
1.719 -
1.720 - retire_cur_alloc_region_common(cur_alloc_region);
1.721 - }
1.722 - assert(_cur_alloc_region == NULL, "post-condition");
1.723 + assert(_mutator_alloc_region.get() == NULL ||
1.724 + !expect_null_mutator_alloc_region,
1.725 + "the current alloc region was unexpectedly found to be non-NULL");
1.726 +
1.727 + if (!isHumongous(word_size)) {
1.728 + return _mutator_alloc_region.attempt_allocation_locked(word_size,
1.729 + false /* bot_updates */);
1.730 + } else {
1.731 + return humongous_obj_allocate(word_size);
1.732 + }
1.733 +
1.734 + ShouldNotReachHere();
1.735 }
1.736
1.737 void G1CollectedHeap::abandon_gc_alloc_regions() {
1.738 @@ -1417,8 +1177,8 @@
1.739
1.740 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1.741 HandleMark hm; // Discard invalid handles created during verification
1.742 + gclog_or_tty->print(" VerifyBeforeGC:");
1.743 prepare_for_verify();
1.744 - gclog_or_tty->print(" VerifyBeforeGC:");
1.745 Universe::verify(true);
1.746 }
1.747
1.748 @@ -1439,9 +1199,8 @@
1.749 concurrent_mark()->abort();
1.750
1.751 // Make sure we'll choose a new allocation region afterwards.
1.752 - abandon_cur_alloc_region();
1.753 + release_mutator_alloc_region();
1.754 abandon_gc_alloc_regions();
1.755 - assert(_cur_alloc_region == NULL, "Invariant.");
1.756 g1_rem_set()->cleanupHRRS();
1.757 tear_down_region_lists();
1.758
1.759 @@ -1547,6 +1306,8 @@
1.760 // evacuation pause.
1.761 clear_cset_fast_test();
1.762
1.763 + init_mutator_alloc_region();
1.764 +
1.765 double end = os::elapsedTime();
1.766 g1_policy()->record_full_collection_end();
1.767
1.768 @@ -1720,8 +1481,9 @@
1.769
1.770 *succeeded = true;
1.771 // Let's attempt the allocation first.
1.772 - HeapWord* result = attempt_allocation_at_safepoint(word_size,
1.773 - false /* expect_null_cur_alloc_region */);
1.774 + HeapWord* result =
1.775 + attempt_allocation_at_safepoint(word_size,
1.776 + false /* expect_null_mutator_alloc_region */);
1.777 if (result != NULL) {
1.778 assert(*succeeded, "sanity");
1.779 return result;
1.780 @@ -1748,7 +1510,7 @@
1.781
1.782 // Retry the allocation
1.783 result = attempt_allocation_at_safepoint(word_size,
1.784 - true /* expect_null_cur_alloc_region */);
1.785 + true /* expect_null_mutator_alloc_region */);
1.786 if (result != NULL) {
1.787 assert(*succeeded, "sanity");
1.788 return result;
1.789 @@ -1765,7 +1527,7 @@
1.790
1.791 // Retry the allocation once more
1.792 result = attempt_allocation_at_safepoint(word_size,
1.793 - true /* expect_null_cur_alloc_region */);
1.794 + true /* expect_null_mutator_alloc_region */);
1.795 if (result != NULL) {
1.796 assert(*succeeded, "sanity");
1.797 return result;
1.798 @@ -1796,7 +1558,7 @@
1.799 if (expand(expand_bytes)) {
1.800 verify_region_sets_optional();
1.801 return attempt_allocation_at_safepoint(word_size,
1.802 - false /* expect_null_cur_alloc_region */);
1.803 + false /* expect_null_mutator_alloc_region */);
1.804 }
1.805 return NULL;
1.806 }
1.807 @@ -1940,7 +1702,6 @@
1.808 _evac_failure_scan_stack(NULL) ,
1.809 _mark_in_progress(false),
1.810 _cg1r(NULL), _summary_bytes_used(0),
1.811 - _cur_alloc_region(NULL),
1.812 _refine_cte_cl(NULL),
1.813 _full_collection(false),
1.814 _free_list("Master Free List"),
1.815 @@ -2099,7 +1860,6 @@
1.816 _g1_max_committed = _g1_committed;
1.817 _hrs = new HeapRegionSeq(_expansion_regions);
1.818 guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
1.819 - guarantee(_cur_alloc_region == NULL, "from constructor");
1.820
1.821 // 6843694 - ensure that the maximum region index can fit
1.822 // in the remembered set structures.
1.823 @@ -2195,6 +1955,22 @@
1.824 // Do later initialization work for concurrent refinement.
1.825 _cg1r->init();
1.826
1.827 + // Here we allocate the dummy full region that is required by the
1.828 + // G1AllocRegion class. If we don't pass an address in the reserved
1.829 + // space here, lots of asserts fire.
1.830 + MemRegion mr(_g1_reserved.start(), HeapRegion::GrainWords);
1.831 + HeapRegion* dummy_region = new HeapRegion(_bot_shared, mr, true);
1.832 + // We'll re-use the same region whether the alloc region will
1.833 + // require BOT updates or not and, if it doesn't, then a non-young
1.834 + // region will complain that it cannot support allocations without
1.835 + // BOT updates. So we'll tag the dummy region as young to avoid that.
1.836 + dummy_region->set_young();
1.837 + // Make sure it's full.
1.838 + dummy_region->set_top(dummy_region->end());
1.839 + G1AllocRegion::setup(this, dummy_region);
1.840 +
1.841 + init_mutator_alloc_region();
1.842 +
1.843 return JNI_OK;
1.844 }
1.845
1.846 @@ -2261,7 +2037,7 @@
1.847 "Should be owned on this thread's behalf.");
1.848 size_t result = _summary_bytes_used;
1.849 // Read only once in case it is set to NULL concurrently
1.850 - HeapRegion* hr = _cur_alloc_region;
1.851 + HeapRegion* hr = _mutator_alloc_region.get();
1.852 if (hr != NULL)
1.853 result += hr->used();
1.854 return result;
1.855 @@ -2324,13 +2100,11 @@
1.856 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
1.857 // to be a problem in the optimized build, since the two loads of the
1.858 // current allocation region field are optimized away.
1.859 - HeapRegion* car = _cur_alloc_region;
1.860 -
1.861 - // FIXME: should iterate over all regions?
1.862 - if (car == NULL) {
1.863 + HeapRegion* hr = _mutator_alloc_region.get();
1.864 + if (hr == NULL) {
1.865 return 0;
1.866 }
1.867 - return car->free();
1.868 + return hr->free();
1.869 }
1.870
1.871 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1.872 @@ -2781,16 +2555,12 @@
1.873 // since we can't allow tlabs to grow big enough to accomodate
1.874 // humongous objects.
1.875
1.876 - // We need to store the cur alloc region locally, since it might change
1.877 - // between when we test for NULL and when we use it later.
1.878 - ContiguousSpace* cur_alloc_space = _cur_alloc_region;
1.879 + HeapRegion* hr = _mutator_alloc_region.get();
1.880 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
1.881 -
1.882 - if (cur_alloc_space == NULL) {
1.883 + if (hr == NULL) {
1.884 return max_tlab_size;
1.885 } else {
1.886 - return MIN2(MAX2(cur_alloc_space->free(), (size_t)MinTLABSize),
1.887 - max_tlab_size);
1.888 + return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
1.889 }
1.890 }
1.891
1.892 @@ -3364,6 +3134,7 @@
1.893 }
1.894
1.895 verify_region_sets_optional();
1.896 + verify_dirty_young_regions();
1.897
1.898 {
1.899 // This call will decide whether this pause is an initial-mark
1.900 @@ -3425,8 +3196,8 @@
1.901
1.902 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1.903 HandleMark hm; // Discard invalid handles created during verification
1.904 + gclog_or_tty->print(" VerifyBeforeGC:");
1.905 prepare_for_verify();
1.906 - gclog_or_tty->print(" VerifyBeforeGC:");
1.907 Universe::verify(false);
1.908 }
1.909
1.910 @@ -3442,7 +3213,7 @@
1.911
1.912 // Forget the current alloc region (we might even choose it to be part
1.913 // of the collection set!).
1.914 - abandon_cur_alloc_region();
1.915 + release_mutator_alloc_region();
1.916
1.917 // The elapsed time induced by the start time below deliberately elides
1.918 // the possible verification above.
1.919 @@ -3573,6 +3344,8 @@
1.920 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
1.921 #endif // YOUNG_LIST_VERBOSE
1.922
1.923 + init_mutator_alloc_region();
1.924 +
1.925 double end_time_sec = os::elapsedTime();
1.926 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
1.927 g1_policy()->record_pause_time_ms(pause_time_ms);
1.928 @@ -3655,6 +3428,15 @@
1.929 return gclab_word_size;
1.930 }
1.931
1.932 +void G1CollectedHeap::init_mutator_alloc_region() {
1.933 + assert(_mutator_alloc_region.get() == NULL, "pre-condition");
1.934 + _mutator_alloc_region.init();
1.935 +}
1.936 +
1.937 +void G1CollectedHeap::release_mutator_alloc_region() {
1.938 + _mutator_alloc_region.release();
1.939 + assert(_mutator_alloc_region.get() == NULL, "post-condition");
1.940 +}
1.941
1.942 void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
1.943 assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose");
1.944 @@ -5140,10 +4922,8 @@
1.945 CardTableModRefBS* _ct_bs;
1.946 public:
1.947 G1VerifyCardTableCleanup(CardTableModRefBS* ct_bs)
1.948 - : _ct_bs(ct_bs)
1.949 - { }
1.950 - virtual bool doHeapRegion(HeapRegion* r)
1.951 - {
1.952 + : _ct_bs(ct_bs) { }
1.953 + virtual bool doHeapRegion(HeapRegion* r) {
1.954 MemRegion mr(r->bottom(), r->end());
1.955 if (r->is_survivor()) {
1.956 _ct_bs->verify_dirty_region(mr);
1.957 @@ -5153,6 +4933,29 @@
1.958 return false;
1.959 }
1.960 };
1.961 +
1.962 +void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
1.963 + CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
1.964 + for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
1.965 + // We cannot guarantee that [bottom(),end()] is dirty. Threads
1.966 + // dirty allocated blocks as they allocate them. The thread that
1.967 + // retires each region and replaces it with a new one will do a
1.968 + // maximal allocation to fill in [pre_dummy_top(),end()] but will
1.969 + // not dirty that area (one less thing to have to do while holding
1.970 + // a lock). So we can only verify that [bottom(),pre_dummy_top()]
1.971 + // is dirty. Also note that verify_dirty_region() requires
1.972 + // mr.start() and mr.end() to be card aligned and pre_dummy_top()
1.973 + // is not guaranteed to be.
1.974 + MemRegion mr(hr->bottom(),
1.975 + ct_bs->align_to_card_boundary(hr->pre_dummy_top()));
1.976 + ct_bs->verify_dirty_region(mr);
1.977 + }
1.978 +}
1.979 +
1.980 +void G1CollectedHeap::verify_dirty_young_regions() {
1.981 + verify_dirty_young_list(_young_list->first_region());
1.982 + verify_dirty_young_list(_young_list->first_survivor_region());
1.983 +}
1.984 #endif
1.985
1.986 void G1CollectedHeap::cleanUpCardTable() {
1.987 @@ -5500,6 +5303,44 @@
1.988 }
1.989 }
1.990
1.991 +HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
1.992 + bool force) {
1.993 + assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1.994 + assert(!force || g1_policy()->can_expand_young_list(),
1.995 + "if force is true we should be able to expand the young list");
1.996 + if (force || !g1_policy()->is_young_list_full()) {
1.997 + HeapRegion* new_alloc_region = new_region(word_size,
1.998 + false /* do_expand */);
1.999 + if (new_alloc_region != NULL) {
1.1000 + g1_policy()->update_region_num(true /* next_is_young */);
1.1001 + set_region_short_lived_locked(new_alloc_region);
1.1002 + return new_alloc_region;
1.1003 + }
1.1004 + }
1.1005 + return NULL;
1.1006 +}
1.1007 +
1.1008 +void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
1.1009 + size_t allocated_bytes) {
1.1010 + assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1.1011 + assert(alloc_region->is_young(), "all mutator alloc regions should be young");
1.1012 +
1.1013 + g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
1.1014 + _summary_bytes_used += allocated_bytes;
1.1015 +}
1.1016 +
1.1017 +HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
1.1018 + bool force) {
1.1019 + return _g1h->new_mutator_alloc_region(word_size, force);
1.1020 +}
1.1021 +
1.1022 +void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
1.1023 + size_t allocated_bytes) {
1.1024 + _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
1.1025 +}
1.1026 +
1.1027 +// Heap region set verification
1.1028 +
1.1029 class VerifyRegionListsClosure : public HeapRegionClosure {
1.1030 private:
1.1031 HumongousRegionSet* _humongous_set;
