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Kernel: Avoid O(n) loop over zones when allocating from PhysicalRegion

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We now keep all the PhysicalZones on one of two intrusive lists within
the PhysicalRegion.

The "usable" list contains all zones that can be allocated from,
and the "full" list contains all zones with no free pages.
This commit is contained in:
Andreas Kling 2021-07-13 19:52:42 +02:00
parent 9ae067aa7f
commit 379bcd26e4
3 changed files with 38 additions and 10 deletions
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34
Kernel/VM/PhysicalRegion.cpp
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@ -47,6 +47,7 @@ void PhysicalRegion::initialize_zones()
m_zones.append(make<PhysicalZone>(base_address, zone_size));
dmesgln(" * Zone {:016x}-{:016x} ({} bytes)", base_address.get(), base_address.get() + zone_size * PAGE_SIZE - 1, zone_size * PAGE_SIZE);
base_address = base_address.offset(zone_size * PAGE_SIZE);
m_usable_zones.append(m_zones.last());
remaining_pages -= zone_size;
}
};
@ -75,9 +76,13 @@ NonnullRefPtrVector<PhysicalPage> PhysicalRegion::take_contiguous_free_pages(siz
Optional<PhysicalAddress> page_base;
for (auto& zone : m_zones) {
page_base = zone.allocate_block(order);
if (page_base.has_value())
if (page_base.has_value()) {
if (zone.is_empty()) {
// We've exhausted this zone, move it to the full zones list.
m_full_zones.append(zone);
}
break;
}
}
if (!page_base.has_value())
@ -93,21 +98,34 @@ NonnullRefPtrVector<PhysicalPage> PhysicalRegion::take_contiguous_free_pages(siz
RefPtr<PhysicalPage> PhysicalRegion::take_free_page()
{
for (auto& zone : m_zones) {
auto page = zone.allocate_block(0);
if (page.has_value())
return PhysicalPage::create(page.value());
if (m_usable_zones.is_empty()) {
dbgln("PhysicalRegion::take_free_page: No free physical pages");
return nullptr;
}
dbgln("PhysicalRegion::take_free_page: No free physical pages");
return nullptr;
auto& zone = *m_usable_zones.first();
auto page = zone.allocate_block(0);
VERIFY(page.has_value());
if (zone.is_empty()) {
// We've exhausted this zone, move it to the full zones list.
m_full_zones.append(zone);
}
return PhysicalPage::create(page.value());
}
void PhysicalRegion::return_page(PhysicalAddress paddr)
{
// FIXME: Find a way to avoid looping over the zones here.
// (Do some math on the address to find the right zone index.)
// The main thing that gets in the way of this is non-uniform zone sizes.
// Perhaps it would be better if all zones had the same size.
for (auto& zone : m_zones) {
if (zone.contains(paddr)) {
zone.deallocate_block(paddr, 0);
if (m_full_zones.contains(zone))
m_usable_zones.append(zone);
return;
}
}