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Subject[PATCH 2/2] I/OAT: tcp_dma_copybreak default value dependant on I/OAT version
Date
I/OAT DMA performance tuning showed different optimal values 
of tcp_dma_copybreak for different I/OAT versions
(4096 for 1.2 and 2048 for 2.0).
This patch lets ioatdma driver set tcp_dma_copybreak value
according to these results.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
---
drivers/dma/dmaengine.c | 3 +++
drivers/dma/ioat_dma.c | 15 +++++++++++++++
include/linux/dmaengine.h | 2 ++
3 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 97b329e..d57365a 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -70,6 +70,7 @@ #include <linux/percpu.h>
#include <linux/rcupdate.h>
#include <linux/mutex.h>
#include <linux/jiffies.h>
+#include <net/tcp.h>

static DEFINE_MUTEX(dma_list_mutex);
static LIST_HEAD(dma_device_list);
@@ -402,6 +403,8 @@ int dma_async_device_register(struct dma
list_add_tail(&device->global_node, &dma_device_list);
mutex_unlock(&dma_list_mutex);

+ sysctl_tcp_dma_copybreak = device->tcp_dma_copybreak;
+
dma_clients_notify_available();

return 0;
diff --git a/drivers/dma/ioat_dma.c b/drivers/dma/ioat_dma.c
index 9c0b90a..42e5bfb 100644
--- a/drivers/dma/ioat_dma.c
+++ b/drivers/dma/ioat_dma.c
@@ -53,6 +53,12 @@ #define WATCHDOG_DELAY round_jiffies(ms
static void ioat_dma_chan_reset_part2(struct work_struct *work);
static void ioat_dma_chan_watchdog(struct work_struct *work);

+/*
+ * default tcp_dma_copybreak values for different IOAT versions
+ */
+#define IOAT1_DEFAULT_TCP_DMA_COPYBREAK 4096
+#define IOAT2_DEFAULT_TCP_DMA_COPYBREAK 2048
+
/* internal functions */
static void ioat_dma_start_null_desc(struct ioat_dma_chan *ioat_chan);
static void ioat_dma_memcpy_cleanup(struct ioat_dma_chan *ioat_chan);
@@ -1571,6 +1577,15 @@ struct ioatdma_device *ioat_dma_probe(st
if (err)
goto err_self_test;

+ switch (device->version) {
+ case IOAT_VER_1_2:
+ device->common.tcp_dma_copybreak = IOAT1_DEFAULT_TCP_DMA_COPYBREAK;
+ break;
+ case IOAT_VER_2_0:
+ device->common.tcp_dma_copybreak = IOAT2_DEFAULT_TCP_DMA_COPYBREAK;
+ break;
+ }
+
dma_async_device_register(&device->common);

INIT_DELAYED_WORK(&device->work, ioat_dma_chan_watchdog);
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index d08a5c5..c09128e 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -251,6 +251,7 @@ struct dma_async_tx_descriptor {
* @global_node: list_head for global dma_device_list
* @cap_mask: one or more dma_capability flags
* @max_xor: maximum number of xor sources, 0 if no capability
+ * @tcp_dma_copybreak: lower limit of TCP socket reads size offloaded by DMA
* @refcount: reference count
* @done: IO completion struct
* @dev_id: unique device ID
@@ -272,6 +273,7 @@ struct dma_device {
struct list_head global_node;
dma_cap_mask_t cap_mask;
int max_xor;
+ int tcp_dma_copybreak;

struct kref refcount;
struct completion done;


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