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Kernel: Remove 1 level of indirection for AnonymousVMObject CoW bitmaps

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Instead of keeping AnonymousVMObject::m_cow_map in an OwnPtr<Bitmap>,
just make the Bitmap a regular value member. This increases the size
of the VMObject by 8 bytes, but removes some of the kmalloc/kfree spam
incurred by sys$fork().
This commit is contained in:
Andreas Kling 2021-03-04 10:05:38 +01:00
parent ddaeb294dc
commit 4515652001
Notes: sideshowbarker 2024-07-18 21:43:58 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/4515652001b
2 changed files with 12 additions and 12 deletions
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22
Kernel/VM/AnonymousVMObject.cpp
View File

@ -336,7 +336,7 @@ size_t AnonymousVMObject::count_needed_commit_pages_for_nonvolatile_range(const
auto range_end = range.base + range.count;
for (size_t page_index = range.base; page_index < range_end; page_index++) {
// COW pages are accounted for in m_shared_committed_cow_pages
if (m_cow_map && m_cow_map->get(page_index))
if (!m_cow_map.is_null() && m_cow_map.get(page_index))
continue;
auto& phys_page = m_physical_pages[page_index];
if (phys_page && phys_page->is_shared_zero_page())
@ -355,7 +355,7 @@ size_t AnonymousVMObject::mark_committed_pages_for_nonvolatile_range(const Volat
auto range_end = range.base + range.count;
for (size_t page_index = range.base; page_index < range_end; page_index++) {
// COW pages are accounted for in m_shared_committed_cow_pages
if (m_cow_map && m_cow_map->get(page_index))
if (!m_cow_map.is_null() && m_cow_map.get(page_index))
continue;
auto& phys_page = m_physical_pages[page_index];
if (phys_page && phys_page->is_shared_zero_page()) {
@ -395,17 +395,17 @@ RefPtr<PhysicalPage> AnonymousVMObject::allocate_committed_page(size_t page_inde
Bitmap& AnonymousVMObject::ensure_cow_map()
{
if (!m_cow_map)
m_cow_map = make<Bitmap>(page_count(), true);
return *m_cow_map;
if (m_cow_map.is_null())
m_cow_map = Bitmap { page_count(), true };
return m_cow_map;
}
void AnonymousVMObject::ensure_or_reset_cow_map()
{
if (!m_cow_map)
m_cow_map = make<Bitmap>(page_count(), true);
if (m_cow_map.is_null())
ensure_cow_map();
else
m_cow_map->fill(true);
m_cow_map.fill(true);
}
bool AnonymousVMObject::should_cow(size_t page_index, bool is_shared) const
@ -415,7 +415,7 @@ bool AnonymousVMObject::should_cow(size_t page_index, bool is_shared) const
return true;
if (is_shared)
return false;
return m_cow_map && m_cow_map->get(page_index);
return !m_cow_map.is_null() && m_cow_map.get(page_index);
}
void AnonymousVMObject::set_should_cow(size_t page_index, bool cow)
@ -425,9 +425,9 @@ void AnonymousVMObject::set_should_cow(size_t page_index, bool cow)
size_t AnonymousVMObject::cow_pages() const
{
if (!m_cow_map)
if (m_cow_map.is_null())
return 0;
return m_cow_map->count_slow(true);
return m_cow_map.count_slow(true);
}
bool AnonymousVMObject::is_nonvolatile(size_t page_index)

2
Kernel/VM/AnonymousVMObject.h
View File

@ -147,7 +147,7 @@ private:
Vector<PurgeablePageRanges*> m_purgeable_ranges;
size_t m_unused_committed_pages { 0 };
mutable OwnPtr<Bitmap> m_cow_map;
Bitmap m_cow_map;
// We share a pool of committed cow-pages with clones
RefPtr<CommittedCowPages> m_shared_committed_cow_pages;