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UserspaceEmulator: Add a page-address-to-MMU-region lookup map

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To make SoftMMU::find_region() O(1), this patch invests 3MiB into a
lookup table where we track each possible page base address and map
them to the SoftMMU::Region corresponding to that address.

This is another large improvement to general emulation performance. :^)
This commit is contained in:
Andreas Kling 2020-11-15 17:30:32 +01:00
parent a4a389156d
commit 59b4874443
Notes: sideshowbarker 2024-07-19 01:22:50 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/59b48744431
2 changed files with 16 additions and 5 deletions
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19
DevTools/UserspaceEmulator/SoftMMU.cpp
View File

@ -37,24 +37,33 @@ SoftMMU::Region* SoftMMU::find_region(X86::LogicalAddress address)
if (address.selector() == 0x28)
return m_tls_region.ptr();
for (auto& region : m_regions) {
if (region.contains(address.offset()))
return &region;
}
return nullptr;
size_t page_index = (address.offset() & ~(PAGE_SIZE - 1)) / PAGE_SIZE;
return m_page_to_region_map[page_index];
}
void SoftMMU::add_region(NonnullOwnPtr<Region> region)
{
ASSERT(!find_region({ 0x20, region->base() }));
// FIXME: More sanity checks pls
if (region->is_shared_buffer())
m_shbuf_regions.set(static_cast<SharedBufferRegion*>(region.ptr())->shbuf_id(), region.ptr());
size_t first_page_in_region = region->base() / PAGE_SIZE;
for (size_t i = 0; i < ceil_div(region->size(), PAGE_SIZE); ++i) {
m_page_to_region_map[first_page_in_region + i] = region.ptr();
}
m_regions.append(move(region));
}
void SoftMMU::remove_region(Region& region)
{
size_t first_page_in_region = region.base() / PAGE_SIZE;
for (size_t i = 0; i < ceil_div(region.size(), PAGE_SIZE); ++i) {
m_page_to_region_map[first_page_in_region + i] = nullptr;
}
if (region.is_shared_buffer())
m_shbuf_regions.remove(static_cast<SharedBufferRegion&>(region).shbuf_id());
m_regions.remove_first_matching([&](auto& entry) { return entry.ptr() == &region; });

2
DevTools/UserspaceEmulator/SoftMMU.h
View File

@ -125,6 +125,8 @@ public:
}
private:
Region* m_page_to_region_map[786432];
OwnPtr<Region> m_tls_region;
NonnullOwnPtrVector<Region> m_regions;
HashMap<int, Region*> m_shbuf_regions;