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Subject[PATCH v2 11/11] vduse: Support specifying bounce buffer size via sysfs
Date
As discussed in [1], this adds sysfs interface to support
specifying bounce buffer size in virtio-vdpa case. It would
be a performance tuning parameter for high throughput workloads.

[1] https://www.spinics.net/lists/netdev/msg754288.html

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
---
drivers/vdpa/vdpa_user/vduse_dev.c | 45 +++++++++++++++++++++++++++++-
1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index bd1ba6c33e09..0458d61cee1f 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -38,8 +38,11 @@
#define DRV_LICENSE "GPL v2"

#define VDUSE_DEV_MAX (1U << MINORBITS)
+#define VDUSE_MAX_BOUNCE_SIZE (1024 * 1024 * 1024)
+#define VDUSE_MIN_BOUNCE_SIZE (1024 * 1024)
#define VDUSE_BOUNCE_SIZE (64 * 1024 * 1024)
-#define VDUSE_IOVA_SIZE (128 * 1024 * 1024)
+/* 128 MB reserved for virtqueue creation */
+#define VDUSE_IOVA_SIZE (VDUSE_MAX_BOUNCE_SIZE + 128 * 1024 * 1024)
#define VDUSE_MSG_DEFAULT_TIMEOUT 30

struct vduse_virtqueue {
@@ -1795,8 +1798,48 @@ static ssize_t msg_timeout_store(struct device *device,

static DEVICE_ATTR_RW(msg_timeout);

+static ssize_t bounce_size_show(struct device *device,
+ struct device_attribute *attr, char *buf)
+{
+ struct vduse_dev *dev = dev_get_drvdata(device);
+
+ return sysfs_emit(buf, "%u\n", dev->bounce_size);
+}
+
+static ssize_t bounce_size_store(struct device *device,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct vduse_dev *dev = dev_get_drvdata(device);
+ unsigned int bounce_size;
+ int ret;
+
+ ret = -EPERM;
+ mutex_lock(&dev->domain_lock);
+ if (dev->domain)
+ goto unlock;
+
+ ret = kstrtouint(buf, 10, &bounce_size);
+ if (ret < 0)
+ goto unlock;
+
+ ret = -EINVAL;
+ if (bounce_size > VDUSE_MAX_BOUNCE_SIZE ||
+ bounce_size < VDUSE_MIN_BOUNCE_SIZE)
+ goto unlock;
+
+ dev->bounce_size = bounce_size & PAGE_MASK;
+ ret = count;
+unlock:
+ mutex_unlock(&dev->domain_lock);
+ return ret;
+}
+
+static DEVICE_ATTR_RW(bounce_size);
+
static struct attribute *vduse_dev_attrs[] = {
&dev_attr_msg_timeout.attr,
+ &dev_attr_bounce_size.attr,
NULL
};

--
2.20.1
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