* Broke the cache merging code out of vm_cache_remove_consumer() into
new function merge_cache_with_only_consumer(), which is also used in vm_cache_remove_area(), now. * Added tracing for the merge case. git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25716 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Ingo Weinhold
parent
0a871009db
commit
ad66253c1a
@ -193,6 +193,27 @@ class RemoveConsumer : public VMCacheTraceEntry {
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};
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class Merge : public VMCacheTraceEntry {
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public:
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Merge(vm_cache* cache, vm_cache* consumer)
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:
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VMCacheTraceEntry(cache),
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fConsumer(consumer)
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{
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Initialized();
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}
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virtual void AddDump(TraceOutput& out)
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{
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out.Print("vm cache merge with consumer: cache: %p, consumer: %p",
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fCache, fConsumer);
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}
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private:
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vm_cache* fConsumer;
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};
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class InsertArea : public VMCacheTraceEntry {
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public:
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InsertArea(vm_cache* cache, vm_area* area)
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@ -359,6 +380,140 @@ delete_cache(vm_cache* cache)
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}
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static bool
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is_cache_mergeable(vm_cache* cache)
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{
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return (cache->areas == NULL && cache->source != NULL
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&& !list_is_empty(&cache->consumers)
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&& cache->consumers.link.next == cache->consumers.link.prev);
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}
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/*! Merges the given cache with its only consumer.
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The caller must own a reference (other than the one from the consumer) and
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hold the cache's lock.
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*/
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static void
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merge_cache_with_only_consumer(vm_cache* cache)
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{
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vm_cache* consumer = (vm_cache*)list_get_first_item(&cache->consumers);
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if (!acquire_unreferenced_cache_ref(consumer))
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return;
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// In case we managed to grab a reference to the consumerRef,
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// this doesn't guarantee that we get the cache we wanted
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// to, so we need to check if this cache is really the last
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// consumer of the cache we want to merge it with.
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ConditionVariable busyCondition;
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// But since we need to keep the locking order upper->lower cache, we
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// need to unlock our cache now
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busyCondition.Publish(cache, "cache");
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cache->busy = true;
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while (true) {
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mutex_unlock(&cache->lock);
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mutex_lock(&consumer->lock);
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mutex_lock(&cache->lock);
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bool isMergeable = is_cache_mergeable(cache);
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if (isMergeable && consumer == list_get_first_item(&cache->consumers))
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break;
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// something changed, get rid of the consumer lock and ref
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mutex_unlock(&consumer->lock);
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vm_cache_release_ref(consumer);
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if (!isMergeable) {
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dprintf("merge_cache_with_only_consumer(): cache %p is no longer; "
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"mergeable\n", cache);
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cache->busy = false;
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busyCondition.Unpublish();
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return;
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}
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// the cache is still mergeable, just the consumer changed
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consumer = (vm_cache*)list_get_first_item(&cache->consumers);
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if (!acquire_unreferenced_cache_ref(consumer))
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return;
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}
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consumer = (vm_cache*)list_remove_head_item(&cache->consumers);
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TRACE(("merge vm cache %p (ref == %ld) with vm cache %p\n",
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cache, cache->ref_count, consumer));
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T(Merge(cache, consumer));
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vm_page* nextPage;
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for (vm_page* page = cache->page_list; page != NULL;
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page = nextPage) {
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vm_page* consumerPage;
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nextPage = page->cache_next;
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consumerPage = vm_cache_lookup_page(consumer,
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(off_t)page->cache_offset << PAGE_SHIFT);
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if (consumerPage == NULL) {
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// the page is not yet in the consumer cache - move it upwards
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vm_cache_remove_page(cache, page);
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vm_cache_insert_page(consumer, page,
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(off_t)page->cache_offset << PAGE_SHIFT);
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} else if (consumerPage->state == PAGE_STATE_BUSY
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&& consumerPage->type == PAGE_TYPE_DUMMY) {
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// the page is currently busy taking a read fault - IOW,
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// vm_soft_fault() has mapped our page so we can just
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// move it up
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//dprintf("%ld: merged busy page %p, cache %p, offset %ld\n", find_thread(NULL), page, cacheRef->cache, page->cache_offset);
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vm_cache_remove_page(consumer, consumerPage);
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consumerPage->state = PAGE_STATE_INACTIVE;
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((vm_dummy_page*)consumerPage)->busy_condition.Unpublish();
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vm_cache_remove_page(cache, page);
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vm_cache_insert_page(consumer, page,
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(off_t)page->cache_offset << PAGE_SHIFT);
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#ifdef DEBUG_PAGE_CACHE_TRANSITIONS
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} else {
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page->debug_flags = 0;
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if (consumerPage->state == PAGE_STATE_BUSY)
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page->debug_flags |= 0x1;
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if (consumerPage->type == PAGE_TYPE_DUMMY)
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page->debug_flags |= 0x2;
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page->collided_page = consumerPage;
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consumerPage->collided_page = page;
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#endif // DEBUG_PAGE_CACHE_TRANSITIONS
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}
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}
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vm_cache* newSource = cache->source;
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// The remaining consumer has got a new source
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mutex_lock(&newSource->lock);
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list_remove_item(&newSource->consumers, cache);
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list_add_item(&newSource->consumers, consumer);
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consumer->source = newSource;
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cache->source = NULL;
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mutex_unlock(&newSource->lock);
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// Release the reference the cache's consumer owned. The consumer takes
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// over the cache's ref to its source instead.
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if (cache->ref_count < 2)
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panic("cacheRef %p ref count too low!\n", cache);
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vm_cache_release_ref(cache);
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cache->busy = false;
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busyCondition.Unpublish();
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mutex_unlock(&consumer->lock);
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vm_cache_release_ref(consumer);
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}
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// #pragma mark -
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@ -750,120 +905,9 @@ vm_cache_remove_consumer(vm_cache* cache, vm_cache* consumer)
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list_remove_item(&cache->consumers, consumer);
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consumer->source = NULL;
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if (cache->areas == NULL && cache->source != NULL
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&& !list_is_empty(&cache->consumers)
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&& cache->consumers.link.next == cache->consumers.link.prev) {
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// The cache is not really needed anymore - it can be merged with its only
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// consumer left.
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consumer = (vm_cache*)list_get_first_item(&cache->consumers);
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bool merge = acquire_unreferenced_cache_ref(consumer);
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// In case we managed to grab a reference to the consumerRef,
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// this doesn't guarantee that we get the cache we wanted
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// to, so we need to check if this cache is really the last
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// consumer of the cache we want to merge it with.
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ConditionVariable busyCondition;
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if (merge) {
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// But since we need to keep the locking order upper->lower cache, we
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// need to unlock our cache now
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busyCondition.Publish(cache, "cache");
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cache->busy = true;
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mutex_unlock(&cache->lock);
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mutex_lock(&consumer->lock);
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mutex_lock(&cache->lock);
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if (cache->areas != NULL || cache->source == NULL
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|| list_is_empty(&cache->consumers)
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|| cache->consumers.link.next != cache->consumers.link.prev
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|| consumer != list_get_first_item(&cache->consumers)) {
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dprintf("vm_cache_remove_consumer(): cache %p was modified; "
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"not merging it\n", cache);
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merge = false;
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cache->busy = false;
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busyCondition.Unpublish();
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mutex_unlock(&consumer->lock);
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vm_cache_release_ref(consumer);
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}
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}
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if (merge) {
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consumer = (vm_cache*)list_remove_head_item(&cache->consumers);
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TRACE(("merge vm cache %p (ref == %ld) with vm cache %p\n",
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cache, cache->ref_count, consumer));
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vm_page* nextPage;
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for (vm_page* page = cache->page_list; page != NULL;
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page = nextPage) {
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vm_page* consumerPage;
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nextPage = page->cache_next;
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consumerPage = vm_cache_lookup_page(consumer,
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(off_t)page->cache_offset << PAGE_SHIFT);
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if (consumerPage == NULL) {
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// the page already is not yet in the consumer cache - move
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// it upwards
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vm_cache_remove_page(cache, page);
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vm_cache_insert_page(consumer, page,
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(off_t)page->cache_offset << PAGE_SHIFT);
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} else if (consumerPage->state == PAGE_STATE_BUSY
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&& consumerPage->type == PAGE_TYPE_DUMMY) {
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// the page is currently busy taking a read fault - IOW,
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// vm_soft_fault() has mapped our page so we can just
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// move it up
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//dprintf("%ld: merged busy page %p, cache %p, offset %ld\n", find_thread(NULL), page, cacheRef->cache, page->cache_offset);
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vm_cache_remove_page(consumer, consumerPage);
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consumerPage->state = PAGE_STATE_INACTIVE;
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((vm_dummy_page*)consumerPage)->busy_condition.Unpublish();
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vm_cache_remove_page(cache, page);
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vm_cache_insert_page(consumer, page,
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(off_t)page->cache_offset << PAGE_SHIFT);
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#ifdef DEBUG_PAGE_CACHE_TRANSITIONS
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} else {
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page->debug_flags = 0;
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if (consumerPage->state == PAGE_STATE_BUSY)
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page->debug_flags |= 0x1;
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if (consumerPage->type == PAGE_TYPE_DUMMY)
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page->debug_flags |= 0x2;
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page->collided_page = consumerPage;
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consumerPage->collided_page = page;
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#endif // DEBUG_PAGE_CACHE_TRANSITIONS
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}
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}
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vm_cache* newSource = cache->source;
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// The remaining consumer has gotten a new source
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mutex_lock(&newSource->lock);
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list_remove_item(&newSource->consumers, cache);
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list_add_item(&newSource->consumers, consumer);
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consumer->source = newSource;
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cache->source = NULL;
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mutex_unlock(&newSource->lock);
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// Release the other reference to the cache - we take over
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// its reference of its source cache; we can do this here
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// (with the cacheRef locked) since we own another reference
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// from the first consumer we removed
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if (cache->ref_count < 2)
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panic("cacheRef %p ref count too low!\n", cache);
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vm_cache_release_ref(cache);
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mutex_unlock(&consumer->lock);
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vm_cache_release_ref(consumer);
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}
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if (cache->busy)
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busyCondition.Unpublish();
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}
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// merge cache, if possible
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if (is_cache_mergeable(cache))
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merge_cache_with_only_consumer(cache);
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mutex_unlock(&cache->lock);
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vm_cache_release_ref(cache);
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@ -937,5 +981,9 @@ vm_cache_remove_area(vm_cache* cache, vm_area* area)
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if (cache->store->ops->release_ref)
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cache->store->ops->release_ref(cache->store);
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// merge cache, if possible
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if (is_cache_mergeable(cache))
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merge_cache_with_only_consumer(cache);
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return B_OK;
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}
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