diff mbox series

[RFC,V3,2/2] net: netvsc: Allocate per-device swiotlb bounce buffer for netvsc

Message ID 20220526120113.971512-3-ltykernel@gmail.com (mailing list archive)
State RFC
Delegated to: Netdev Maintainers
Headers show
Series swiotlb: Add child io tlb mem support | expand

Checks

Context Check Description
netdev/tree_selection success Guessing tree name failed - patch did not apply

Commit Message

Tianyu Lan May 26, 2022, 12:01 p.m. UTC 
From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Netvsc driver allocates device io tlb mem via calling swiotlb_device_
allocate() and set child io tlb mem number according to device queue
number. Child io tlb mem may reduce overhead of single spin lock in
device io tlb mem among multi device queues.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
 drivers/net/hyperv/netvsc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Tianyu Lan May 27, 2022, 12:20 p.m. UTC | #1 
On 5/27/2022 2:43 AM, Dexuan Cui wrote:
>> From: Tianyu Lan <ltykernel@gmail.com>
>> Sent: Thursday, May 26, 2022 5:01 AM
>> ...
>> @@ -119,6 +124,10 @@ static void netvsc_subchan_work(struct work_struct
>> *w)
>>   			nvdev->max_chn = 1;
>>   			nvdev->num_chn = 1;
>>   		}
>> +
>> +		/* Allocate boucne buffer.*/
>> +		swiotlb_device_allocate(&hdev->device, nvdev->num_chn,
>> +				10 * IO_TLB_BLOCK_UNIT);
>>   	}
> 
> Looks like swiotlb_device_allocate() is not called if the netvsc device
> has only 1 primary channel and no sub-schannel, e.g. in the case of
> single-vCPU VM?

When there is only sinlge，there seems not to be much performance
penalty. But you are right, we should keep the same behavior when single 
CPU and multi CPU. Will update in the next version.

Thanks.
diff mbox series

Patch

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 9442f751ad3a..26a8f8f84fc4 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -23,6 +23,7 @@ 
 
 #include <asm/sync_bitops.h>
 #include <asm/mshyperv.h>
+#include <linux/swiotlb.h>
 
 #include "hyperv_net.h"
 #include "netvsc_trace.h"
@@ -98,6 +99,7 @@  static void netvsc_subchan_work(struct work_struct *w)
 	struct netvsc_device *nvdev =
 		container_of(w, struct netvsc_device, subchan_work);
 	struct rndis_device *rdev;
+	struct hv_device *hdev;
 	int i, ret;
 
 	/* Avoid deadlock with device removal already under RTNL */
@@ -108,6 +110,9 @@  static void netvsc_subchan_work(struct work_struct *w)
 
 	rdev = nvdev->extension;
 	if (rdev) {
+		hdev = ((struct net_device_context *)
+			netdev_priv(rdev->ndev))->device_ctx;
+
 		ret = rndis_set_subchannel(rdev->ndev, nvdev, NULL);
 		if (ret == 0) {
 			netif_device_attach(rdev->ndev);
@@ -119,6 +124,10 @@  static void netvsc_subchan_work(struct work_struct *w)
 			nvdev->max_chn = 1;
 			nvdev->num_chn = 1;
 		}
+
+		/* Allocate boucne buffer.*/
+		swiotlb_device_allocate(&hdev->device, nvdev->num_chn,
+				10 * IO_TLB_BLOCK_UNIT);
 	}
 
 	rtnl_unlock();
@@ -769,6 +778,7 @@  void netvsc_device_remove(struct hv_device *device)
 
 	/* Release all resources */
 	free_netvsc_device_rcu(net_device);
+	swiotlb_device_free(&device->device);
 }
 
 #define RING_AVAIL_PERCENT_HIWATER 20