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https://github.com/SerenityOS/serenity
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aee9317d86
This significantly reduces the pressure on the kernel heap when allocating a lot of pages. Previously at about 250MB allocated, the free page list would outgrow the kernel's heap. Given that there is no longer a page list, this does not happen. The next barrier will be the kernel memory used by the page records for in-use memory. This kicks in at about 1GB.
78 lines
1.7 KiB
C++
78 lines
1.7 KiB
C++
#include <AK/Bitmap.h>
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#include <AK/Retained.h>
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#include <AK/RetainPtr.h>
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#include <Kernel/Assertions.h>
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#include <Kernel/PhysicalAddress.h>
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#include <Kernel/VM/PhysicalPage.h>
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#include <Kernel/VM/PhysicalRegion.h>
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Retained<PhysicalRegion> PhysicalRegion::create(PhysicalAddress lower, PhysicalAddress upper)
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{
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return adopt(*new PhysicalRegion(lower, upper));
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}
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PhysicalRegion::PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper)
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: m_lower(lower)
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, m_upper(upper)
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, m_bitmap(Bitmap::create())
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{
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}
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void PhysicalRegion::expand(PhysicalAddress lower, PhysicalAddress upper)
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{
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ASSERT(!m_pages);
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m_lower = lower;
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m_upper = upper;
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}
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unsigned PhysicalRegion::finalize_capacity()
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{
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ASSERT(!m_pages);
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m_pages = (m_upper.get() - m_lower.get()) / PAGE_SIZE;
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m_bitmap.grow(m_pages, false);
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return size();
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}
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RetainPtr<PhysicalPage> PhysicalRegion::take_free_page(bool supervisor)
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{
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ASSERT(m_pages);
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if (m_used == m_pages)
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return nullptr;
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for (unsigned page = m_last; page < m_pages; page++) {
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if (!m_bitmap.get(page)) {
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m_bitmap.set(page, true);
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m_used++;
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m_last = page + 1;
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return PhysicalPage::create(m_lower.offset(page * PAGE_SIZE), supervisor);
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}
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}
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ASSERT_NOT_REACHED();
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return nullptr;
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}
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void PhysicalRegion::return_page_at(PhysicalAddress addr)
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{
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ASSERT(m_pages);
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if (m_used == 0) {
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ASSERT_NOT_REACHED();
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}
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int local_offset = addr.get() - m_lower.get();
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ASSERT(local_offset >= 0);
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ASSERT(local_offset < m_pages * PAGE_SIZE);
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auto page = local_offset / PAGE_SIZE;
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if (page < m_last) m_last = page;
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m_bitmap.set(page, false);
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m_used--;
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}
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