Mercurial > hg > truffle
diff src/share/vm/gc_implementation/g1/g1AllocRegion.cpp @ 2433:abdfc822206f
7023069: G1: Introduce symmetric locking in the slow allocation path
7023151: G1: refactor the code that operates on _cur_alloc_region to be re-used for allocs by the GC threads
7018286: G1: humongous allocation attempts should take the GC locker into account
Summary: First, this change replaces the asymmetric locking scheme in the G1 slow alloc path by a summetric one. Second, it factors out the code that operates on _cur_alloc_region so that it can be re-used for allocations by the GC threads in the future.
Reviewed-by: stefank, brutisso, johnc
author | tonyp |
---|---|
date | Wed, 30 Mar 2011 10:26:59 -0400 |
parents | |
children | f44782f04dd4 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/g1/g1AllocRegion.cpp Wed Mar 30 10:26:59 2011 -0400 @@ -0,0 +1,208 @@ +/* + * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + * + */ + +#include "precompiled.hpp" +#include "gc_implementation/g1/g1AllocRegion.inline.hpp" +#include "gc_implementation/g1/g1CollectedHeap.inline.hpp" + +G1CollectedHeap* G1AllocRegion::_g1h = NULL; +HeapRegion* G1AllocRegion::_dummy_region = NULL; + +void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) { + assert(_dummy_region == NULL, "should be set once"); + assert(dummy_region != NULL, "pre-condition"); + assert(dummy_region->free() == 0, "pre-condition"); + + // Make sure that any allocation attempt on this region will fail + // and will not trigger any asserts. + assert(allocate(dummy_region, 1, false) == NULL, "should fail"); + assert(par_allocate(dummy_region, 1, false) == NULL, "should fail"); + assert(allocate(dummy_region, 1, true) == NULL, "should fail"); + assert(par_allocate(dummy_region, 1, true) == NULL, "should fail"); + + _g1h = g1h; + _dummy_region = dummy_region; +} + +void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region, + bool bot_updates) { + assert(alloc_region != NULL && alloc_region != _dummy_region, + "pre-condition"); + + // Other threads might still be trying to allocate using a CAS out + // of the region we are trying to retire, as they can do so without + // holding the lock. So, we first have to make sure that noone else + // can allocate out of it by doing a maximal allocation. Even if our + // CAS attempt fails a few times, we'll succeed sooner or later + // given that failed CAS attempts mean that the region is getting + // closed to being full. + size_t free_word_size = alloc_region->free() / HeapWordSize; + + // This is the minimum free chunk we can turn into a dummy + // object. If the free space falls below this, then noone can + // allocate in this region anyway (all allocation requests will be + // of a size larger than this) so we won't have to perform the dummy + // allocation. + size_t min_word_size_to_fill = CollectedHeap::min_fill_size(); + + while (free_word_size >= min_word_size_to_fill) { + HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates); + if (dummy != NULL) { + // If the allocation was successful we should fill in the space. + CollectedHeap::fill_with_object(dummy, free_word_size); + alloc_region->set_pre_dummy_top(dummy); + break; + } + + free_word_size = alloc_region->free() / HeapWordSize; + // It's also possible that someone else beats us to the + // allocation and they fill up the region. In that case, we can + // just get out of the loop. + } + assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill, + "post-condition"); +} + +void G1AllocRegion::retire(bool fill_up) { + assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly")); + + trace("retiring"); + HeapRegion* alloc_region = _alloc_region; + if (alloc_region != _dummy_region) { + // We never have to check whether the active region is empty or not, + // and potentially free it if it is, given that it's guaranteed that + // it will never be empty. + assert(!alloc_region->is_empty(), + ar_ext_msg(this, "the alloc region should never be empty")); + + if (fill_up) { + fill_up_remaining_space(alloc_region, _bot_updates); + } + + assert(alloc_region->used() >= _used_bytes_before, + ar_ext_msg(this, "invariant")); + size_t allocated_bytes = alloc_region->used() - _used_bytes_before; + retire_region(alloc_region, allocated_bytes); + _used_bytes_before = 0; + _alloc_region = _dummy_region; + } + trace("retired"); +} + +HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size, + bool force) { + assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition")); + assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition")); + + trace("attempting region allocation"); + HeapRegion* new_alloc_region = allocate_new_region(word_size, force); + if (new_alloc_region != NULL) { + new_alloc_region->reset_pre_dummy_top(); + // Need to do this before the allocation + _used_bytes_before = new_alloc_region->used(); + HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates); + assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded")); + + OrderAccess::storestore(); + // Note that we first perform the allocation and then we store the + // region in _alloc_region. This is the reason why an active region + // can never be empty. + _alloc_region = new_alloc_region; + trace("region allocation successful"); + return result; + } else { + trace("region allocation failed"); + return NULL; + } + ShouldNotReachHere(); +} + +void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) { + msg->append("[%s] %s b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT, + _name, message, BOOL_TO_STR(_bot_updates), + _alloc_region, _used_bytes_before); +} + +void G1AllocRegion::init() { + trace("initializing"); + assert(_alloc_region == NULL && _used_bytes_before == 0, + ar_ext_msg(this, "pre-condition")); + assert(_dummy_region != NULL, "should have been set"); + _alloc_region = _dummy_region; + trace("initialized"); +} + +HeapRegion* G1AllocRegion::release() { + trace("releasing"); + HeapRegion* alloc_region = _alloc_region; + retire(false /* fill_up */); + assert(_alloc_region == _dummy_region, "post-condition of retire()"); + _alloc_region = NULL; + trace("released"); + return (alloc_region == _dummy_region) ? NULL : alloc_region; +} + +#if G1_ALLOC_REGION_TRACING +void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) { + // All the calls to trace that set either just the size or the size + // and the result are considered part of level 2 tracing and are + // skipped during level 1 tracing. + if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) { + const size_t buffer_length = 128; + char hr_buffer[buffer_length]; + char rest_buffer[buffer_length]; + + HeapRegion* alloc_region = _alloc_region; + if (alloc_region == NULL) { + jio_snprintf(hr_buffer, buffer_length, "NULL"); + } else if (alloc_region == _dummy_region) { + jio_snprintf(hr_buffer, buffer_length, "DUMMY"); + } else { + jio_snprintf(hr_buffer, buffer_length, + HR_FORMAT, HR_FORMAT_PARAMS(alloc_region)); + } + + if (G1_ALLOC_REGION_TRACING > 1) { + if (result != NULL) { + jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT, + word_size, result); + } else if (word_size != 0) { + jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size); + } else { + jio_snprintf(rest_buffer, buffer_length, ""); + } + } else { + jio_snprintf(rest_buffer, buffer_length, ""); + } + + tty->print_cr("[%s] %s : %s %s", _name, hr_buffer, str, rest_buffer); + } +} +#endif // G1_ALLOC_REGION_TRACING + +G1AllocRegion::G1AllocRegion(const char* name, + bool bot_updates) + : _name(name), _bot_updates(bot_updates), + _alloc_region(NULL), _used_bytes_before(0) { } +