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Kernel: Make PhysicalRegion::return_page() do arithmetic instead of loop

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Most of the time, we will be freeing physical pages within the
full-sized zones. We can do some simple math to find the right zone
immediately instead of looping through the zones, checking each one.

We still do loop through the slack/remainder zones at the end.
There's probably an even nicer way to solve this, but this is already a
nice improvement. :^)
This commit is contained in:
Andreas Kling 2021-12-11 19:00:47 +01:00
parent 63117f826b
commit 259cca456f
Notes: sideshowbarker 2024-07-17 22:58:59 +09:00
2 changed files with 21 additions and 8 deletions
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26
Kernel/Memory/PhysicalRegion.cpp
View file

@ -42,7 +42,8 @@ void PhysicalRegion::initialize_zones()
size_t remaining_pages = m_pages;
auto base_address = m_lower;
auto make_zones = [&](size_t pages_per_zone) {
auto make_zones = [&](size_t zone_size) {
size_t pages_per_zone = zone_size / PAGE_SIZE;
size_t zone_count = 0;
auto first_address = base_address;
while (remaining_pages >= pages_per_zone) {
@ -57,10 +58,10 @@ void PhysicalRegion::initialize_zones()
};
// First make 16 MiB zones (with 4096 pages each)
make_zones(4096);
make_zones(large_zone_size);
// Then divide any remaining space into 1 MiB zones (with 256 pages each)
make_zones(256);
make_zones(small_zone_size);
}
OwnPtr<PhysicalRegion> PhysicalRegion::try_take_pages_from_beginning(unsigned page_count)
@ -122,11 +123,20 @@ RefPtr<PhysicalPage> PhysicalRegion::take_free_page()
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) {
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);
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;
}
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))

3
Kernel/Memory/PhysicalRegion.h
View file

@ -41,6 +41,9 @@ public:
private:
PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper);
static constexpr size_t large_zone_size = 16 * MiB;
static constexpr size_t small_zone_size = 1 * MiB;
NonnullOwnPtrVector<PhysicalZone> m_zones;
PhysicalZone::List m_usable_zones;