From 1bcf7d8ae698be75e3ee9189d4f7c15267abfd35 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nils=20O=2E=20Sel=C3=A5sdal?= <nos@utel.tech>
Date: Tue, 9 Jun 2026 19:56:34 +0200
Subject: [PATCH] Optimize arena_push() to do 1 commit when pushed size is
 larger than commit siz

---
 src/arena.c | 55 +++++++++++++++++++++++++++++++++++------------------
 src/arena.h |  1 +
 2 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/src/arena.c b/src/arena.c
index e3bdf23..9891c05 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -2,44 +2,57 @@
 #include "base_core.h"
 #include "platform.h"
 
-
-static MemoryBlock *memoryblock_allocate(U32 size, U32 commit_size, U32 page_size)
+typedef struct MemoryBlockOptions MemoryBlockOptions;
+struct MemoryBlockOptions {
+    U32 size;
+    U32 commit_size;
+    U32 commit_now_size;
+    U32 page_size;
+};
+static U32 idx;
+static MemoryBlock *memoryblock_allocate(const MemoryBlockOptions *opts)
 {
-    U32 aligned_size        = AlignUpPow2(size, page_size);
-    U32 aligned_commit_size = AlignUpPow2(commit_size, page_size);
+    U32 aligned_size            = AlignUpPow2(opts->size, opts->page_size);
+    U32 aligned_commit_size     = AlignUpPow2(opts->commit_size, opts->page_size);
+    U32 aligned_commit_now_size = AlignUpPow2(opts->commit_now_size, opts->page_size);
 
     MemoryBlock *block = memory_reserve(aligned_size);
     Assert(block != NULL);
-    memory_commit(block, aligned_commit_size);
+    memory_commit(block, aligned_commit_now_size);
 
     block->base          = (U8 *)block;
     block->size          = aligned_size;
     block->first_free    = MemoryBlock_Header_Size;
     block->arena_offset  = 0;
     block->prev          = NULL;
-    block->committed_end = aligned_commit_size;
+    block->committed_end = aligned_commit_now_size;
+    block->idx = idx++;
 
     ASAN_POISON_MEMORY_REGION(block->base, block->size);
     ASAN_UNPOISON_MEMORY_REGION(block, MemoryBlock_Header_Size);
     return block;
 }
 
-void arena_init(Arena *arena, const ArenaOptions *params)
+void arena_init(Arena *arena, const ArenaOptions *opts)
 {
     U32 page_size = platform_page_size();
-    Assert(params->size > MemoryBlock_Header_Size);
-    Assert(params->size < (U32_Max -  page_size)); // Reserving last piece so our math doesn't overflow
-    Assert(params->commit_size > 0);
-    Assert(params->commit_size <= params->size);
+    Assert(opts->size > MemoryBlock_Header_Size);
+    Assert(opts->size < (U32_Max -  page_size)); // Reserving last piece so our math doesn't overflow
+    Assert(opts->commit_size > 0);
+    Assert(opts->commit_size <= opts->size);
 
+    MemoryBlockOptions mb_opts;
+    mb_opts.page_size       = page_size;
+    mb_opts.commit_size     = opts->commit_size;
+    mb_opts.size            = opts->size;
+    mb_opts.commit_now_size = opts->commit_size;
+    MemoryBlock *block = memoryblock_allocate(&mb_opts);
 
-    MemoryBlock *block = memoryblock_allocate(params->size, params->commit_size, page_size);
-
-    arena->flags            = params->flags;
+    arena->flags            = opts->flags;
     arena->checkpoint_level = 0;
     arena->current          = block;
-    arena->block_size       = params->size;
-    arena->commit_size      = params->commit_size;
+    arena->block_size       = opts->size;
+    arena->commit_size      = opts->commit_size;
     arena->page_size        = page_size;
 
 }
@@ -72,9 +85,15 @@ void *arena_push(Arena *arena, U32 size, U32 align)
             block_size = AlignUpPow2(size + MemoryBlock_Header_Size,align);
             new_commit_size = block_size;
         }
+        U32 commit_now_size = Max(new_commit_size, size);
 
-        MemoryBlock *new_block  = memoryblock_allocate(block_size, new_commit_size, arena->page_size);
-        // base_pos tracks the virtual absolute position within an arena
+        MemoryBlockOptions mb_opts;
+        mb_opts.page_size   = arena->page_size;
+        mb_opts.commit_size = new_commit_size;
+        mb_opts.size        = block_size;
+        mb_opts.commit_now_size = commit_now_size;
+        MemoryBlock *new_block = memoryblock_allocate(&mb_opts);
+        // arena_offset tracks the virtual absolute position within an arena
         // This is not a contiguous space, we use it to free blocks when popping the arena
         new_block->arena_offset = block->arena_offset + block->size;
         new_block->prev         = block;
diff --git a/src/arena.h b/src/arena.h
index 934c2c8..239e7f9 100644
--- a/src/arena.h
+++ b/src/arena.h
@@ -18,6 +18,7 @@ struct MemoryBlock {
     U64 arena_offset;   // absolute offset of base relative to the first linked arena
     U32 committed_end;  // end of committed region. Will be page aligned
     MemoryBlock *prev;
+    U32 idx;
 };
 
 typedef struct Arena Arena;