[Intel-wired-lan] [RESEND PATCH net-next 1/2] e1000: Remove unnecessary use of kmap_atomic()

[Intel-wired-lan] [RESEND PATCH net-next 1/2] e1000: Remove unnecessary use of kmap_atomic()

[Anirudh Venkataramanan]

buffer_info->rxbuf.page accessed in e1000_clean_jumbo_rx_irq() is
allocated using GFP_ATOMIC. Pages allocated with GFP_ATOMIC can't come from
highmem and so there's no need to kmap() them. Just use page_address().

I don't have access to a 32-bit system so did some limited testing on
qemu (qemu-system-i386 -m 4096 -smp 4 -device e1000e) with a 32-bit
Debian 11.04 image.

Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
---
 drivers/net/ethernet/intel/e1000/e1000_main.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 23299fc..93e57b1 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -4229,8 +4229,6 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter,
 				 */
 				p = buffer_info->rxbuf.page;
 				if (length <= copybreak) {
-					u8 *vaddr;
-
 					if (likely(!(netdev->features & NETIF_F_RXFCS)))
 						length -= 4;
 					skb = e1000_alloc_rx_skb(adapter,
@@ -4238,10 +4236,9 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter,
 					if (!skb)
 						break;
 
-					vaddr = kmap_atomic(p);
-					memcpy(skb_tail_pointer(skb), vaddr,
-					       length);
-					kunmap_atomic(vaddr);
+					memcpy(skb_tail_pointer(skb),
+					       page_address(p), length);
+
 					/* re-use the page, so don't erase
 					 * buffer_info->rxbuf.page
 					 */
-- 
2.37.2

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[Intel-wired-lan] [RESEND PATCH net-next 2/2] e1000e: Remove unnecessary use of kmap_atomic()

[Anirudh Venkataramanan]

alloc_rx_buf() allocates ps_page->page and buffer_info->page using either
GFP_ATOMIC or GFP_KERNEL. Memory allocated with GFP_KERNEL/GFP_ATOMIC can't
come from highmem and so there's no need to kmap() them. Just use
page_address().

I don't have access to a 32-bit system so did some limited testing on qemu
(qemu-system-i386 -m 4096 -smp 4 -device e1000e) with a 32-bit Debian 11.04
image.

Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 321f2a9..05a59e5 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -1393,21 +1393,14 @@ static bool e1000_clean_rx_irq_ps(struct e1000_ring *rx_ring, int *work_done,
 			 */
 			if (l1 && (l1 <= copybreak) &&
 			    ((length + l1) <= adapter->rx_ps_bsize0)) {
-				u8 *vaddr;
-
 				ps_page = &buffer_info->ps_pages[0];
 
-				/* there is no documentation about how to call
-				 * kmap_atomic, so we can't hold the mapping
-				 * very long
-				 */
 				dma_sync_single_for_cpu(&pdev->dev,
 							ps_page->dma,
 							PAGE_SIZE,
 							DMA_FROM_DEVICE);
-				vaddr = kmap_atomic(ps_page->page);
-				memcpy(skb_tail_pointer(skb), vaddr, l1);
-				kunmap_atomic(vaddr);
+				memcpy(skb_tail_pointer(skb),
+				       page_address(ps_page->page), l1);
 				dma_sync_single_for_device(&pdev->dev,
 							   ps_page->dma,
 							   PAGE_SIZE,
@@ -1607,11 +1600,9 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_ring *rx_ring, int *work_done,
 				 */
 				if (length <= copybreak &&
 				    skb_tailroom(skb) >= length) {
-					u8 *vaddr;
-					vaddr = kmap_atomic(buffer_info->page);
-					memcpy(skb_tail_pointer(skb), vaddr,
+					memcpy(skb_tail_pointer(skb),
+					       page_address(buffer_info->page),
 					       length);
-					kunmap_atomic(vaddr);
 					/* re-use the page, so don't erase
 					 * buffer_info->page
 					 */
-- 
2.37.2

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Re: [Intel-wired-lan] [RESEND PATCH net-next 1/2] e1000: Remove unnecessary use of kmap_atomic()

[Ira Weiny]

On Mon, Sep 19, 2022 at 11:09:48AM -0700, Venkataramanan, Anirudh wrote:
> buffer_info->rxbuf.page accessed in e1000_clean_jumbo_rx_irq() is
> allocated using GFP_ATOMIC. Pages allocated with GFP_ATOMIC can't come from
> highmem and so there's no need to kmap() them. Just use page_address().
> 
> I don't have access to a 32-bit system so did some limited testing on
> qemu (qemu-system-i386 -m 4096 -smp 4 -device e1000e) with a 32-bit
> Debian 11.04 image.
> 
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
> Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
> ---
>  drivers/net/ethernet/intel/e1000/e1000_main.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
> index 23299fc..93e57b1 100644
> --- a/drivers/net/ethernet/intel/e1000/e1000_main.c
> +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
> @@ -4229,8 +4229,6 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter,
>  				 */
>  				p = buffer_info->rxbuf.page;
>  				if (length <= copybreak) {
> -					u8 *vaddr;
> -
>  					if (likely(!(netdev->features & NETIF_F_RXFCS)))
>  						length -= 4;
>  					skb = e1000_alloc_rx_skb(adapter,
> @@ -4238,10 +4236,9 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter,
>  					if (!skb)
>  						break;
>  
> -					vaddr = kmap_atomic(p);
> -					memcpy(skb_tail_pointer(skb), vaddr,
> -					       length);
> -					kunmap_atomic(vaddr);
> +					memcpy(skb_tail_pointer(skb),
> +					       page_address(p), length);
> +
>  					/* re-use the page, so don't erase
>  					 * buffer_info->rxbuf.page
>  					 */
> -- 
> 2.37.2
> 
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Re: [Intel-wired-lan] [RESEND PATCH net-next 2/2] e1000e: Remove unnecessary use of kmap_atomic()

[Ira Weiny]

On Mon, Sep 19, 2022 at 11:09:49AM -0700, Venkataramanan, Anirudh wrote:
> alloc_rx_buf() allocates ps_page->page and buffer_info->page using either
> GFP_ATOMIC or GFP_KERNEL. Memory allocated with GFP_KERNEL/GFP_ATOMIC can't
> come from highmem and so there's no need to kmap() them. Just use
> page_address().
> 
> I don't have access to a 32-bit system so did some limited testing on qemu
> (qemu-system-i386 -m 4096 -smp 4 -device e1000e) with a 32-bit Debian 11.04
> image.
> 
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
> Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
> ---
>  drivers/net/ethernet/intel/e1000e/netdev.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index 321f2a9..05a59e5 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -1393,21 +1393,14 @@ static bool e1000_clean_rx_irq_ps(struct e1000_ring *rx_ring, int *work_done,
>  			 */

The comment just above here says this:

1389                         /* page alloc/put takes too long and effects small                     
1390                          * packet throughput, so unsplit small packets and
1391                          * save the alloc/put only valid in softirq (napi)
1392                          * context to call kmap_*
1393                          */

I'm unable to grok what that means exactly but I feel like the kmap part is no
longer appropriate?

Maybe just delete ... 'to call kmap_*'?

The code itself looks ok.  With some clean up to that comment:

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

Ira

>  			if (l1 && (l1 <= copybreak) &&
>  			    ((length + l1) <= adapter->rx_ps_bsize0)) {
> -				u8 *vaddr;
> -
>  				ps_page = &buffer_info->ps_pages[0];
>  
> -				/* there is no documentation about how to call
> -				 * kmap_atomic, so we can't hold the mapping
> -				 * very long
> -				 */
>  				dma_sync_single_for_cpu(&pdev->dev,
>  							ps_page->dma,
>  							PAGE_SIZE,
>  							DMA_FROM_DEVICE);
> -				vaddr = kmap_atomic(ps_page->page);
> -				memcpy(skb_tail_pointer(skb), vaddr, l1);
> -				kunmap_atomic(vaddr);
> +				memcpy(skb_tail_pointer(skb),
> +				       page_address(ps_page->page), l1);
>  				dma_sync_single_for_device(&pdev->dev,
>  							   ps_page->dma,
>  							   PAGE_SIZE,
> @@ -1607,11 +1600,9 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_ring *rx_ring, int *work_done,
>  				 */
>  				if (length <= copybreak &&
>  				    skb_tailroom(skb) >= length) {
> -					u8 *vaddr;
> -					vaddr = kmap_atomic(buffer_info->page);
> -					memcpy(skb_tail_pointer(skb), vaddr,
> +					memcpy(skb_tail_pointer(skb),
> +					       page_address(buffer_info->page),
>  					       length);
> -					kunmap_atomic(vaddr);
>  					/* re-use the page, so don't erase
>  					 * buffer_info->page
>  					 */
> -- 
> 2.37.2
> 
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Re: [Intel-wired-lan] [RESEND PATCH net-next 2/2] e1000e: Remove unnecessary use of kmap_atomic()

[Anirudh Venkataramanan]

On 9/29/2022 3:40 PM, Ira Weiny wrote:
> On Mon, Sep 19, 2022 at 11:09:49AM -0700, Venkataramanan, Anirudh wrote:
>> alloc_rx_buf() allocates ps_page->page and buffer_info->page using either
>> GFP_ATOMIC or GFP_KERNEL. Memory allocated with GFP_KERNEL/GFP_ATOMIC can't
>> come from highmem and so there's no need to kmap() them. Just use
>> page_address().
>>
>> I don't have access to a 32-bit system so did some limited testing on qemu
>> (qemu-system-i386 -m 4096 -smp 4 -device e1000e) with a 32-bit Debian 11.04
>> image.
>>
>> Cc: Ira Weiny <ira.weiny@intel.com>
>> Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
>> Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
>> Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
>> Suggested-by: Ira Weiny <ira.weiny@intel.com>
>> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
>> Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
>> ---
>>   drivers/net/ethernet/intel/e1000e/netdev.c | 17 ++++-------------
>>   1 file changed, 4 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
>> index 321f2a9..05a59e5 100644
>> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
>> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
>> @@ -1393,21 +1393,14 @@ static bool e1000_clean_rx_irq_ps(struct e1000_ring *rx_ring, int *work_done,
>>   			 */
> 
> The comment just above here says this:
> 
> 1389                         /* page alloc/put takes too long and effects small
> 1390                          * packet throughput, so unsplit small packets and
> 1391                          * save the alloc/put only valid in softirq (napi)
> 1392                          * context to call kmap_*
> 1393                          */

I did see this when I was making the code change but it evaporated from 
my working memory. Thanks for catching it.

> 
> I'm unable to grok what that means exactly but I feel like the kmap part is no
> longer appropriate?
> 
> Maybe just delete ... 'to call kmap_*'?

Okay, so did some git archeology and found that the original comment 
just said this:

/* page alloc/put takes too long and effects small packet
  * throughput, so unsplit small packets and save the alloc/put*/

...  which is what I think we need to revert to.

Tony, do you want me to send a v2? Or is making an inline edit to the 
patch you've already applied to dev-tree less work for you?

I am okay either way. Just tell me which one makes life easier for you.

Thanks!
Ani
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Re: [Intel-wired-lan] [RESEND PATCH net-next 2/2] e1000e: Remove unnecessary use of kmap_atomic()

[Tony Nguyen]

On 9/30/2022 11:20 AM, Anirudh Venkataramanan wrote:
> Tony, do you want me to send a v2? Or is making an inline edit to the 
> patch you've already applied to dev-tree less work for you?
> 
> I am okay either way. Just tell me which one makes life easier for you.

v2 would be great.

Thanks,
Tony
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