From 6f38ce8f47f3c086720eb1adc7a855a3bf91a7d1 Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gbeutner@serenityos.org>
Date: Wed, 2 Jun 2021 21:26:09 +0200
Subject: [PATCH] Kernel: Avoid allocations in the VMObject constructor

This avoids allocations in the VMObject constructor. The number of
inline elements was determined empirically and covers most common cases
including LibC malloc.
---
 Kernel/VM/VMObject.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Kernel/VM/VMObject.h b/Kernel/VM/VMObject.h
index 493708aaef0..64de251ef69 100644
--- a/Kernel/VM/VMObject.h
+++ b/Kernel/VM/VMObject.h
@@ -42,8 +42,8 @@ public:
     virtual bool is_contiguous() const { return false; }
 
     size_t page_count() const { return m_physical_pages.size(); }
-    const Vector<RefPtr<PhysicalPage>>& physical_pages() const { return m_physical_pages; }
-    Vector<RefPtr<PhysicalPage>>& physical_pages() { return m_physical_pages; }
+    const Vector<RefPtr<PhysicalPage>, 16>& physical_pages() const { return m_physical_pages; }
+    Vector<RefPtr<PhysicalPage>, 16>& physical_pages() { return m_physical_pages; }
 
     size_t size() const { return m_physical_pages.size() * PAGE_SIZE; }
 
@@ -71,7 +71,7 @@ protected:
     void for_each_region(Callback);
 
     IntrusiveListNode<VMObject> m_list_node;
-    Vector<RefPtr<PhysicalPage>> m_physical_pages;
+    Vector<RefPtr<PhysicalPage>, 16> m_physical_pages;
     Lock m_paging_lock { "VMObject" };
 
     mutable SpinLock<u8> m_lock;