From ec990882b0da2030af2eaf59accd2b613e6d022a Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Sun, 27 Sep 2015 16:50:12 +0200
Subject: [PATCH] Limit extfs device cache to 10% of system memory.

---
 ext/block.cpp  | 23 +++++++++++++++++++----
 ext/block.h    |  3 +++
 ext/device.cpp | 50 ++++++++++++++++++++++++++++++++++++++------------
 ext/device.h   |  3 +++
 4 files changed, 63 insertions(+), 16 deletions(-)

diff --git a/ext/block.cpp b/ext/block.cpp
index b8400dfd..4b6b3f54 100644
--- a/ext/block.cpp
+++ b/ext/block.cpp
@@ -31,7 +31,17 @@
 #include "device.h"
 #include "ioleast.h"
 
+Block::Block()
+{
+	this->block_data = NULL;
+}
+
 Block::Block(Device* device, uint32_t block_id)
+{
+	Construct(device, block_id);
+}
+
+void Block::Construct(Device* device, uint32_t block_id)
 {
 	this->modify_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
 	this->transit_done_cond = PTHREAD_COND_INITIALIZER;
@@ -46,14 +56,18 @@ Block::Block(Device* device, uint32_t block_id)
 	this->block_id = block_id;
 	this->dirty = false;
 	this->is_in_transit = false;
-	this->block_data = NULL;
 }
 
 Block::~Block()
+{
+	Destruct();
+	delete[] block_data;
+}
+
+void Block::Destruct()
 {
 	Sync();
 	Unlink();
-	delete[] block_data;
 }
 
 void Block::Refer()
@@ -64,11 +78,12 @@ void Block::Refer()
 void Block::Unref()
 {
 	if ( !--reference_count )
+	{
 #if 0
+		device->block_count--;
 		delete this;
-#else
-		{};
 #endif
+	}
 }
 
 void Block::Sync()
diff --git a/ext/block.h b/ext/block.h
index 2b1be84e..84381c27 100644
--- a/ext/block.h
+++ b/ext/block.h
@@ -28,8 +28,11 @@ class Device;
 class Block
 {
 public:
+	Block();
 	Block(Device* device, uint32_t block_id);
 	~Block();
+	void Construct(Device* device, uint32_t block_id);
+	void Destruct();
 
 public:
 	pthread_mutex_t modify_lock;
diff --git a/ext/device.cpp b/ext/device.cpp
index e85b81c4..b0c6ac14 100644
--- a/ext/device.cpp
+++ b/ext/device.cpp
@@ -61,6 +61,15 @@ Device::Device(int fd, const char* path, uint32_t block_size, bool write)
 	this->has_sync_thread = false;
 	this->sync_thread_should_exit = false;
 	this->sync_in_transit = false;
+	this->block_count = 0;
+#ifdef __sortix__
+	// TODO: This isn't scaleable if there's multiple filesystems mounted.
+	size_t memory;
+	memstat(NULL, &memory);
+	this->block_limit = (memory / 10) / block_size;
+#else
+	this->block_limit = 32768;
+#endif
 }
 
 Device::~Device()
@@ -88,17 +97,37 @@ void Device::SpawnSyncThread()
 		pthread_create(&this->sync_thread, NULL, Device__SyncThread, this) == 0;
 }
 
+Block* Device::AllocateBlock()
+{
+	if ( block_limit <= block_count )
+	{
+		for ( Block* block = lru_block; block; block = block->prev_block )
+		{
+			if ( block->reference_count )
+				continue;
+			block->Destruct(); // Syncs.
+			return block;
+		}
+	}
+	uint8_t* data = new uint8_t[block_size];
+	if ( !data ) // TODO: Use operator new nothrow!
+		return NULL;
+	Block* block = new Block();
+	if ( !block ) // TODO: Use operator new nothrow!
+		return delete[] data, (Block*) NULL;
+	block->block_data = data;
+	block_count++;
+	return block;
+}
+
 Block* Device::GetBlock(uint32_t block_id)
 {
 	if ( Block* block = GetCachedBlock(block_id) )
 		return block;
-	uint8_t* data = new uint8_t[block_size];
-	if ( !data ) // TODO: Use operator new nothrow!
+	Block* block = AllocateBlock();
+	if ( !block )
 		return NULL;
-	Block* block = new Block(this, block_id);
-	if ( !block ) // TODO: Use operator new nothrow!
-		return delete[] data, (Block*) NULL;
-	block->block_data = data;
+	block->Construct(this, block_id);
 	off_t file_offset = (off_t) block_size * (off_t) block_id;
 	preadall(fd, block->block_data, block_size, file_offset);
 	block->Prelink();
@@ -115,13 +144,10 @@ Block* Device::GetBlockZeroed(uint32_t block_id)
 		block->FinishWrite();
 		return block;
 	}
-	uint8_t* data = new uint8_t[block_size];
-	if ( !data ) // TODO: Use operator new nothrow!
+	Block* block = AllocateBlock();
+	if ( !block )
 		return NULL;
-	Block* block = new Block(this, block_id);
-	if ( !block ) // TODO: Use operator new nothrow!
-		return delete[] data, (Block*) NULL;
-	block->block_data = data;
+	block->Construct(this, block_id);
 	memset(block->block_data, 0, block_size);
 	block->Prelink();
 	block->BeginWrite();
diff --git a/ext/device.h b/ext/device.h
index 586f3307..c52fa04e 100644
--- a/ext/device.h
+++ b/ext/device.h
@@ -50,9 +50,12 @@ public:
 	bool has_sync_thread;
 	bool sync_thread_should_exit;
 	bool sync_in_transit;
+	size_t block_count;
+	size_t block_limit;
 
 public:
 	void SpawnSyncThread();
+	Block* AllocateBlock();
 	Block* GetBlock(uint32_t block_id);
 	Block* GetBlockZeroed(uint32_t block_id);
 	Block* GetCachedBlock(uint32_t block_id);