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Kernel: Replace final loop in PhysicalRegion::return_page() with math

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Since it's possible to determine where the small zones will start to
occur for each PhysicalRegion, we can use arithmetic so that the call
time for both large and small zones is identical.
This commit is contained in:
Clay Freeman 2021-12-12 15:00:29 -06:00 • committed by Andreas Kling
parent edb810f854
commit e3e40cca65
2 changed files with 19 additions and 24 deletions
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40
Kernel/Memory/PhysicalRegion.cpp
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@ -42,7 +42,7 @@ void PhysicalRegion::initialize_zones()
size_t remaining_pages = m_pages;
auto base_address = m_lower;
auto make_zones = [&](size_t zone_size) {
auto make_zones = [&](size_t zone_size) -> size_t {
size_t pages_per_zone = zone_size / PAGE_SIZE;
size_t zone_count = 0;
auto first_address = base_address;
@ -55,13 +55,14 @@ void PhysicalRegion::initialize_zones()
}
if (zone_count)
dmesgln(" * {}x PhysicalZone ({} MiB) @ {:016x}-{:016x}", zone_count, pages_per_zone / 256, first_address.get(), base_address.get() - pages_per_zone * PAGE_SIZE - 1);
return zone_count;
};
// First make 16 MiB zones (with 4096 pages each)
make_zones(large_zone_size);
m_large_zones = make_zones(large_zone_size);
// Then divide any remaining space into 1 MiB zones (with 256 pages each)
make_zones(small_zone_size);
m_small_zones = make_zones(small_zone_size);
}
OwnPtr<PhysicalRegion> PhysicalRegion::try_take_pages_from_beginning(unsigned page_count)
@ -123,29 +124,20 @@ RefPtr<PhysicalPage> PhysicalRegion::take_free_page()
void PhysicalRegion::return_page(PhysicalAddress paddr)
{
size_t full_size_zone_index = (paddr.get() - lower().get()) / large_zone_size;
size_t large_zone_count = m_pages / (large_zone_size / PAGE_SIZE);
auto large_zone_base = lower().get();
auto small_zone_base = lower().get() + (m_large_zones * large_zone_size);
if (full_size_zone_index < large_zone_count) {
auto& zone = m_zones[full_size_zone_index];
VERIFY(zone.contains(paddr));
zone.deallocate_block(paddr, 0);
if (m_full_zones.contains(zone))
m_usable_zones.append(zone);
return;
}
size_t zone_index;
if (paddr.get() < small_zone_base)
zone_index = (paddr.get() - large_zone_base) / large_zone_size;
else
zone_index = m_large_zones + (paddr.get() - small_zone_base) / small_zone_size;
for (size_t i = large_zone_count; i < m_zones.size(); ++i) {
auto& zone = m_zones[i];
if (zone.contains(paddr)) {
zone.deallocate_block(paddr, 0);
if (m_full_zones.contains(zone))
m_usable_zones.append(zone);
return;
}
}
VERIFY_NOT_REACHED();
auto& zone = m_zones[zone_index];
VERIFY(zone.contains(paddr));
zone.deallocate_block(paddr, 0);
if (m_full_zones.contains(zone))
m_usable_zones.append(zone);
}
}