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Date: Tue, 6 Dec 2016 09:10:17 -0800
From: Alexander Duyck <alexander.duyck@...il.com>
To: tndave <tushar.n.dave@...cle.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
Netdev <netdev@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [RFC PATCH] i40e: enable PCIe relax ordering
for SPARC
On Mon, Dec 5, 2016 at 2:23 PM, tndave <tushar.n.dave@...cle.com> wrote:
>
>
> On 12/05/2016 01:54 PM, Alexander Duyck wrote:
>>
>> On Mon, Dec 5, 2016 at 9:07 AM, Tushar Dave <tushar.n.dave@...cle.com>
>> wrote:
>>>
>>> Unlike previous generation NIC (e.g. ixgbe) i40e doesn't seem to have
>>> standard CSR where PCIe relaxed ordering can be set. Without PCIe relax
>>> ordering enabled, i40e performance is significantly low on SPARC.
>>>
>>> This patch sets PCIe relax ordering for SPARC arch by setting dma attr
>>> DMA_ATTR_WEAK_ORDERING for every tx and rx DMA map/unmap.
>>> This has shown 10x increase in performance numbers.
>>>
>>> e.g.
>>> iperf TCP test with 10 threads on SPARC S7
>>>
>>> Test 1: Without this patch
>>>
>>> # iperf -s
>>> ------------------------------------------------------------
>>> Server listening on TCP port 5001
>>> TCP window size: 85.3 KByte (default)
>>> ------------------------------------------------------------
>>> [ 4] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40926
>>> [ 5] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40934
>>> [ 6] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40930
>>> [ 7] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40928
>>> [ 8] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40922
>>> [ 9] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40932
>>> [ 10] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40920
>>> [ 11] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40924
>>> [ 14] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40982
>>> [ 12] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 40980
>>> [ ID] Interval Transfer Bandwidth
>>> [ 4] 0.0-20.0 sec 566 MBytes 237 Mbits/sec
>>> [ 5] 0.0-20.0 sec 532 MBytes 223 Mbits/sec
>>> [ 6] 0.0-20.0 sec 537 MBytes 225 Mbits/sec
>>> [ 8] 0.0-20.0 sec 546 MBytes 229 Mbits/sec
>>> [ 11] 0.0-20.0 sec 592 MBytes 248 Mbits/sec
>>> [ 7] 0.0-20.0 sec 539 MBytes 226 Mbits/sec
>>> [ 9] 0.0-20.0 sec 572 MBytes 240 Mbits/sec
>>> [ 10] 0.0-20.0 sec 604 MBytes 253 Mbits/sec
>>> [ 14] 0.0-20.0 sec 567 MBytes 238 Mbits/sec
>>> [ 12] 0.0-20.0 sec 511 MBytes 214 Mbits/sec
>>> [SUM] 0.0-20.0 sec 5.44 GBytes 2.33 Gbits/sec
>>>
>>> Test 2: with this patch:
>>>
>>> # iperf -s
>>> ------------------------------------------------------------
>>> Server listening on TCP port 5001
>>> TCP window size: 85.3 KByte (default)
>>> ------------------------------------------------------------
>>> TCP: request_sock_TCP: Possible SYN flooding on port 5001. Sending
>>> cookies. Check SNMP counters.
>>> [ 4] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46876
>>> [ 5] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46874
>>> [ 6] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46872
>>> [ 7] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46880
>>> [ 8] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46878
>>> [ 9] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46884
>>> [ 10] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46886
>>> [ 11] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46890
>>> [ 12] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46888
>>> [ 13] local 16.0.0.7 port 5001 connected with 16.0.0.1 port 46882
>>> [ ID] Interval Transfer Bandwidth
>>> [ 4] 0.0-20.0 sec 7.45 GBytes 3.19 Gbits/sec
>>> [ 5] 0.0-20.0 sec 7.48 GBytes 3.21 Gbits/sec
>>> [ 7] 0.0-20.0 sec 7.34 GBytes 3.15 Gbits/sec
>>> [ 8] 0.0-20.0 sec 7.42 GBytes 3.18 Gbits/sec
>>> [ 9] 0.0-20.0 sec 7.24 GBytes 3.11 Gbits/sec
>>> [ 10] 0.0-20.0 sec 7.40 GBytes 3.17 Gbits/sec
>>> [ 12] 0.0-20.0 sec 7.49 GBytes 3.21 Gbits/sec
>>> [ 6] 0.0-20.0 sec 7.30 GBytes 3.13 Gbits/sec
>>> [ 11] 0.0-20.0 sec 7.44 GBytes 3.19 Gbits/sec
>>> [ 13] 0.0-20.0 sec 7.22 GBytes 3.10 Gbits/sec
>>> [SUM] 0.0-20.0 sec 73.8 GBytes 31.6 Gbits/sec
>>>
>>> NOTE: In my testing, this patch does _not_ show any harm to i40e
>>> performance numbers on x86.
>>>
>>> Signed-off-by: Tushar Dave <tushar.n.dave@...cle.com>
>>
>>
>> You went through and replaced all of the dma_unmap/map_page calls with
>> dma_map/unmap_single_attrs I would prefer you didn't do that. I have
>
> Yes, because currently there is no DMA API for dma_map/unmap_page with dma
> attr*
>>
>> patches to add the ability to map and unmap pages with attributes that
>> should be available for 4.10-rc1 so if you could wait on this patch
>> until then it would be preferred.
>
> :-) thanks. I will wait until your patches are out.
>
>>
>>> ---
>>> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 69
>>> ++++++++++++++++++++---------
>>> drivers/net/ethernet/intel/i40e/i40e_txrx.h | 1 +
>>> 2 files changed, 49 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> index 6287bf6..800dca7 100644
>>> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
>>> @@ -551,15 +551,17 @@ static void i40e_unmap_and_free_tx_resource(struct
>>> i40e_ring *ring,
>>> else
>>> dev_kfree_skb_any(tx_buffer->skb);
>>> if (dma_unmap_len(tx_buffer, len))
>>> - dma_unmap_single(ring->dev,
>>> - dma_unmap_addr(tx_buffer, dma),
>>> - dma_unmap_len(tx_buffer, len),
>>> - DMA_TO_DEVICE);
>>> + dma_unmap_single_attrs(ring->dev,
>>> + dma_unmap_addr(tx_buffer,
>>> dma),
>>> + dma_unmap_len(tx_buffer,
>>> len),
>>> + DMA_TO_DEVICE,
>>> + ring->dma_attrs);
>>> } else if (dma_unmap_len(tx_buffer, len)) {
>>> - dma_unmap_page(ring->dev,
>>> - dma_unmap_addr(tx_buffer, dma),
>>> - dma_unmap_len(tx_buffer, len),
>>> - DMA_TO_DEVICE);
>>> + dma_unmap_single_attrs(ring->dev,
>>> + dma_unmap_addr(tx_buffer, dma),
>>> + dma_unmap_len(tx_buffer, len),
>>> + DMA_TO_DEVICE,
>>> + ring->dma_attrs);
>>> }
>>>
>>> tx_buffer->next_to_watch = NULL;
>>> @@ -662,6 +664,8 @@ static bool i40e_clean_tx_irq(struct i40e_vsi *vsi,
>>> struct i40e_tx_buffer *tx_buf;
>>> struct i40e_tx_desc *tx_head;
>>> struct i40e_tx_desc *tx_desc;
>>> + dma_addr_t addr;
>>> + size_t size;
>>> unsigned int total_bytes = 0, total_packets = 0;
>>> unsigned int budget = vsi->work_limit;
>>>
>>> @@ -696,10 +700,11 @@ static bool i40e_clean_tx_irq(struct i40e_vsi *vsi,
>>> napi_consume_skb(tx_buf->skb, napi_budget);
>>>
>>> /* unmap skb header data */
>>> - dma_unmap_single(tx_ring->dev,
>>> - dma_unmap_addr(tx_buf, dma),
>>> - dma_unmap_len(tx_buf, len),
>>> - DMA_TO_DEVICE);
>>> + dma_unmap_single_attrs(tx_ring->dev,
>>> + dma_unmap_addr(tx_buf, dma),
>>> + dma_unmap_len(tx_buf, len),
>>> + DMA_TO_DEVICE,
>>> + tx_ring->dma_attrs);
>>>
>>> /* clear tx_buffer data */
>>> tx_buf->skb = NULL;
>>> @@ -717,12 +722,15 @@ static bool i40e_clean_tx_irq(struct i40e_vsi *vsi,
>>> tx_desc = I40E_TX_DESC(tx_ring, 0);
>>> }
>>>
>>> + addr = dma_unmap_addr(tx_buf, dma);
>>> + size = dma_unmap_len(tx_buf, len);
>>
>>
>> On some architectures this change could lead to issues since
>> dma_unmap_len could be 0 meaning that addr would never be used.
>
> I see. Thanks.
>
>>
>>> /* unmap any remaining paged data */
>>> if (dma_unmap_len(tx_buf, len)) {
>>> - dma_unmap_page(tx_ring->dev,
>>> - dma_unmap_addr(tx_buf,
>>> dma),
>>> - dma_unmap_len(tx_buf,
>>> len),
>>> - DMA_TO_DEVICE);
>>> + dma_unmap_single_attrs(tx_ring->dev,
>>> + addr,
>>> + size,
>>> + DMA_TO_DEVICE,
>>> +
>>> tx_ring->dma_attrs);
>>> dma_unmap_len_set(tx_buf, len, 0);
>>> }
>>> }
>>> @@ -1010,6 +1018,11 @@ int i40e_setup_tx_descriptors(struct i40e_ring
>>> *tx_ring)
>>> */
>>> tx_ring->size += sizeof(u32);
>>> tx_ring->size = ALIGN(tx_ring->size, 4096);
>>> +#ifdef CONFIG_SPARC
>>> + tx_ring->dma_attrs = DMA_ATTR_WEAK_ORDERING;
>>> +#else
>>> + tx_ring->dma_attrs = 0;
>>> +#endif
>>> tx_ring->desc = dma_alloc_coherent(dev, tx_ring->size,
>>> &tx_ring->dma, GFP_KERNEL);
>>> if (!tx_ring->desc) {
>>
>>
>> Also not a fan of adding yet ring attribute. Is there any reason why
>> you couldn't simply add a set of inline functions at the start of
>> i40e_txrx.c that could replace the DMA map/unmap operations in this
>> code but pass either 0 or DMA_ATTR_WEAK_ORDERING as needed for the
>> drivers? Then the x86 code doesn't have to change while the SPARC
>> code will be able to be passed the attribute.
>
> Sure I can do that.
>
> I will follow up with patch after your patches for map/unmap page with dma
> attr will be out.
>
> Thanks.
>
> -Tushar
>
I was thinking about it and I realized we can probably simplify this
even further. In the case of most other architectures the
DMA_ATTR_WEAK_ORDERING has no effect anyway. So from what I can tell
there is probably no reason not to just always pass that attribute
with the DMA mappings. From what I can tell the only other
architecture that uses this is the PowerPC Cell architecture.
Also I was wondering if you actually needed to enable this attribute
for both Rx and Tx buffers or just Rx buffers? The patch that enabled
DMA_ATTR_WEAK_ORDERING for Sparc64 seems to call out writes, but I
didn't see anything about reads. I'm just wondering if changing the
code for Tx has any effect? If not you could probably drop those
changes and just focus on Rx.
Thanks.
- Alex
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