From e76856a4a5d2d03d6bf6bc21362de534a1e774a0 Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Mon, 26 Apr 2010 16:56:37 +0000
Subject: [PATCH] Enabled the IOCache depending on the amount of free pages.
 Currently the limit is 180 MB.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36495 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 .../drivers/disk/scsi/scsi_cd/scsi_cd.cpp     | 26 ++++++++++++-------
 .../drivers/disk/scsi/scsi_cd/scsi_cd.h       |  8 +-----
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.cpp b/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.cpp
index eae1bd2692..bfc2e148a8 100644
--- a/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.cpp
+++ b/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.cpp
@@ -19,6 +19,7 @@
 #include <string.h>
 
 #include <io_requests.h>
+#include <vm/vm_page.h>
 
 #include "IOCache.h"
 #include "IOSchedulerSimple.h"
@@ -887,13 +888,22 @@ cd_set_capacity(cd_driver_info* info, uint64 capacity, uint32 blockSize)
 		if (status != B_OK)
 			panic("initializing DMAResource failed: %s", strerror(status));
 
-#if USE_IO_CACHE
-		info->io_scheduler = new(std::nothrow) IOCache(info->dma_resource,
-			1024 * 1024);
-#else
-		info->io_scheduler = new(std::nothrow) IOSchedulerSimple(
-			info->dma_resource);
-#endif
+		// Allocate the I/O scheduler. If there seems to be sufficient memory
+		// we use an IOCache, since that adds caching at the lowest I/O layer
+		// and thus dramatically reduces I/O operations and seeks. The
+		// disadvantage is that it increases free memory (physical pages)
+		// fragmentation, which makes large contiguous allocations more likely
+		// to fail.
+		size_t freeMemory = vm_page_num_free_pages();
+		if (freeMemory > 180 * 1024 * 1024 / B_PAGE_SIZE) {
+			info->io_scheduler = new(std::nothrow) IOCache(info->dma_resource,
+				1024 * 1024);
+		} else {
+			dprintf("scsi_cd: Using IOSchedulerSimple instead of IOCache to "
+				"avoid memory allocation issues.\n");
+			info->io_scheduler = new(std::nothrow) IOSchedulerSimple(
+				info->dma_resource);
+		}
 
 		if (info->io_scheduler == NULL)
 			panic("allocating IOScheduler failed.");
@@ -906,10 +916,8 @@ cd_set_capacity(cd_driver_info* info, uint64 capacity, uint32 blockSize)
 		info->io_scheduler->SetCallback(do_io, info);
 	}
 
-#if USE_IO_CACHE
 	if (info->io_scheduler != NULL)
 		info->io_scheduler->SetDeviceCapacity(capacity * blockSize);
-#endif
 
 	info->block_size = blockSize;
 }
diff --git a/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.h b/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.h
index 632f2bd952..b683e79f44 100644
--- a/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.h
+++ b/src/add-ons/kernel/drivers/disk/scsi/scsi_cd/scsi_cd.h
@@ -14,6 +14,7 @@
 #include "dma_resources.h"
 #include "IORequest.h"
 
+
 struct IOCache;
 struct IOScheduler;
 
@@ -21,20 +22,13 @@ struct IOScheduler;
 #define SCSI_CD_DRIVER_MODULE_NAME "drivers/disk/scsi/scsi_cd/driver_v1"
 #define SCSI_CD_DEVICE_MODULE_NAME "drivers/disk/scsi/scsi_cd/device_v1"
 
-// enables using the IOCache instead of the IOScheduler
-#define USE_IO_CACHE	0
-
 
 struct cd_driver_info {
 	device_node*			node;
 	::scsi_periph_device	scsi_periph_device;
 	::scsi_device			scsi_device;
 	scsi_device_interface*	scsi;
-#if USE_IO_CACHE
-	IOCache*				io_scheduler;
-#else
 	IOScheduler*			io_scheduler;
-#endif
 	DMAResource*			dma_resource;
 
 	uint64					capacity;