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* Decoupled the page_thief() from the low memory handler chain. This is

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necessary because low memory handlers might need to wait for other services
  while we need to make sure the page thief can always steal pages.
* Made the page thief more aggressive when memory is critical: added a third
  run where it will also steal a small amount of active pages to keep things
  going.
* The page thief did not maintain the cache's reference correctly in all
  situations.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22382 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2007-09-30 09:36:28 +00:00
parent 212ad3266b
commit b15c9adec7
1 changed files with 112 additions and 64 deletions
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176
src/system/kernel/vm/vm_page.cpp
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@ -61,6 +61,7 @@ static size_t sReservedPages;
static ConditionVariable<page_queue> sFreePageCondition;
static spinlock sPageLock;
static sem_id sThiefWaitSem;
static sem_id sWriterWaitSem;
@ -713,7 +714,7 @@ page_writer(void* /*unused*/)
locker.Unlock();
//dprintf("write page %p\n", page);
//dprintf("write page %p, cache %p (%ld)\n", page, page->cache, page->cache->ref_count);
vm_clear_map_flags(page, PAGE_MODIFIED);
vm_cache_acquire_ref(page->cache);
pages[numPages++] = page;
@ -759,79 +760,123 @@ page_writer(void* /*unused*/)
}
static void
page_thief(void* /*unused*/, int32 level)
static status_t
page_thief(void* /*unused*/)
{
uint32 steal;
int32 score;
bigtime_t timeout = B_INFINITE_TIMEOUT;
switch (level) {
default:
case B_LOW_MEMORY_NOTE:
steal = 10;
score = -20;
break;
case B_LOW_MEMORY_WARNING:
steal = 50;
score = -5;
break;
case B_LOW_MEMORY_CRITICAL:
steal = 500;
score = -1;
break;
}
while (true) {
acquire_sem_etc(sThiefWaitSem, 1, B_RELATIVE_TIMEOUT, timeout);
vm_page* page = NULL;
InterruptsSpinLocker locker(sPageLock);
int32 state = vm_low_memory_state();
uint32 steal;
int32 score;
switch (state) {
default:
timeout = B_INFINITE_TIMEOUT;
continue;
while (steal > 0) {
if (!locker.IsLocked())
locker.Lock();
// find a candidate to steal from the inactive queue
for (int32 i = sActivePageQueue.count; i-- > 0;) {
// move page to the tail of the queue so that we don't
// scan it again directly
page = dequeue_page(&sActivePageQueue);
enqueue_page(&sActivePageQueue, page);
if (page->state == PAGE_STATE_INACTIVE
&& page->usage_count <= score)
case B_LOW_MEMORY_NOTE:
steal = 10;
score = -20;
timeout = 1000000;
break;
case B_LOW_MEMORY_WARNING:
steal = 50;
score = -5;
timeout = 1000000;
break;
case B_LOW_MEMORY_CRITICAL:
steal = 500;
score = -1;
timeout = 100000;
break;
}
//dprintf("page thief running - target %ld...\n", steal);
if (page == NULL) {
if (score == 0)
break;
vm_page* page = NULL;
bool stealActive = false;
InterruptsSpinLocker locker(sPageLock);
score = 0;
continue;
}
while (steal > 0) {
if (!locker.IsLocked())
locker.Lock();
locker.Unlock();
// find a candidate to steal from the inactive queue
// try to lock the page's cache
for (int32 i = sActivePageQueue.count; i-- > 0;) {
// move page to the tail of the queue so that we don't
// scan it again directly
page = dequeue_page(&sActivePageQueue);
enqueue_page(&sActivePageQueue, page);
vm_cache* cache = vm_cache_acquire_page_cache_ref(page);
if (cache == NULL)
continue;
if ((page->state == PAGE_STATE_INACTIVE
|| stealActive && page->state == PAGE_STATE_ACTIVE)
&& page->usage_count <= score)
break;
}
if (mutex_trylock(&cache->lock) != B_OK
|| page->state != PAGE_STATE_INACTIVE) {
if (page == NULL) {
if (score == 0) {
if (state != B_LOW_MEMORY_CRITICAL)
break;
if (stealActive && score > 5)
break;
// when memory is really low, we really want pages
if (stealActive)
score = 127;
else {
stealActive = true;
score = 5;
steal = 5;
}
continue;
}
score = 0;
continue;
}
locker.Unlock();
// try to lock the page's cache
vm_cache* cache = vm_cache_acquire_page_cache_ref(page);
if (cache == NULL)
continue;
if (mutex_trylock(&cache->lock) != B_OK) {
vm_cache_release_ref(cache);
continue;
}
if (page->state != PAGE_STATE_INACTIVE) {
mutex_unlock(&cache->lock);
vm_cache_release_ref(cache);
continue;
}
// we can now steal this page
//dprintf(" steal page %p from cache %p\n", page, cache);
vm_remove_all_page_mappings(page);
vm_cache_remove_page(cache, page);
vm_page_set_state(page, PAGE_STATE_FREE);
steal--;
mutex_unlock(&cache->lock);
vm_cache_release_ref(cache);
continue;
}
// we can now steal this page
vm_cache_remove_page(cache, page);
vm_page_set_state(page, PAGE_STATE_FREE);
steal--;
mutex_unlock(&cache->lock);
vm_cache_release_ref(cache);
}
return B_OK;
}
static void
schedule_page_thief(void* /*unused*/, int32 level)
{
release_sem(sThiefWaitSem);
}
@ -878,9 +923,7 @@ vm_page_write_modified_pages(vm_cache *cache, bool fsReenter)
vm_clear_map_flags(page, PAGE_MODIFIED);
mutex_unlock(&cache->lock);
status_t status = write_page(page, fsReenter);
mutex_lock(&cache->lock);
InterruptsSpinLocker locker(&sPageLock);
@ -1032,20 +1075,25 @@ vm_page_init_post_thread(kernel_args *args)
thread_id thread;
// create a kernel thread to clear out pages
thread = spawn_kernel_thread(&page_scrubber, "page scrubber", B_LOWEST_ACTIVE_PRIORITY, NULL);
thread = spawn_kernel_thread(&page_scrubber, "page scrubber",
B_LOWEST_ACTIVE_PRIORITY, NULL);
send_signal_etc(thread, SIGCONT, B_DO_NOT_RESCHEDULE);
new (&sFreePageCondition) ConditionVariable<page_queue>;
sFreePageCondition.Publish(&sFreePageQueue, "free page");
register_low_memory_handler(page_thief, NULL, 0);
sWriterWaitSem = create_sem(0, "page writer");
sThiefWaitSem = create_sem(0, "page thief");
thread = spawn_kernel_thread(&page_writer, "page writer",
B_LOW_PRIORITY, NULL);
send_signal_etc(thread, SIGCONT, B_DO_NOT_RESCHEDULE);
thread = spawn_kernel_thread(&page_thief, "page thief",
B_LOW_PRIORITY, NULL);
send_signal_etc(thread, SIGCONT, B_DO_NOT_RESCHEDULE);
register_low_memory_handler(schedule_page_thief, NULL, 100);
return B_OK;
}