diff mbox

[dpdk-dev,1/2] net/sfc: free mbufs in bulks on EF10 native Tx datapath reap

Message ID 1504880151-15394-1-git-send-email-arybchenko@solarflare.com (mailing list archive)
State Superseded, archived
Delegated to: Ferruh Yigit
Headers

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK

Commit Message

Andrew Rybchenko Sept. 8, 2017, 2:15 p.m. UTC 
  From: Ivan Malov <ivan.malov@oktetlabs.ru>

Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
 drivers/net/sfc/sfc_ef10_tx.c | 48 ++++++++++++++++++++++++++++++++++++-------
 drivers/net/sfc/sfc_tweak.h   |  3 +++
 2 files changed, 44 insertions(+), 7 deletions(-)

Comments

Ferruh Yigit Sept. 12, 2017, 6:26 p.m. UTC | #1 
On 9/8/2017 3:15 PM, Andrew Rybchenko wrote:
> From: Ivan Malov <ivan.malov@oktetlabs.ru>
> 
> Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
> ---
>  drivers/net/sfc/sfc_ef10_tx.c | 48 ++++++++++++++++++++++++++++++++++++-------
>  drivers/net/sfc/sfc_tweak.h   |  3 +++
>  2 files changed, 44 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/sfc/sfc_ef10_tx.c b/drivers/net/sfc/sfc_ef10_tx.c
> index 182fc23..5127a7a 100644
> --- a/drivers/net/sfc/sfc_ef10_tx.c
> +++ b/drivers/net/sfc/sfc_ef10_tx.c
> @@ -158,17 +158,35 @@ struct sfc_ef10_txq {
>  	pending += sfc_ef10_tx_process_events(txq);
>  
>  	if (pending != completed) {
> +		struct rte_mbuf *bulk[SFC_TX_REAP_BULK_SIZE];
> +		unsigned int nb = 0;
> +
>  		do {
>  			struct sfc_ef10_tx_sw_desc *txd;
> +			struct rte_mbuf *m;
>  
>  			txd = &txq->sw_ring[completed & ptr_mask];
> +			if (txd->mbuf == NULL)
> +				continue;
>  
> -			if (txd->mbuf != NULL) {
> -				rte_pktmbuf_free(txd->mbuf);
> -				txd->mbuf = NULL;
> +			m = rte_pktmbuf_prefree_seg(txd->mbuf);
> +			txd->mbuf = NULL;
> +			if (m == NULL)
> +				continue;
> +
> +			if ((nb == RTE_DIM(bulk)) ||
> +			    ((nb != 0) && (m->pool != bulk[0]->pool))) {

ICC is giving warning [1] here, as far as I can see this is false
positive but can you please double check in case I am missing something?

And unless if you don't see a way to convince icc without effecting
performance, would you mind updating patch to ignore warning [2] ?


[1]
error #3656: variable "bulk" may be used before its value is set

[2]
  diff --git a/drivers/net/sfc/Makefile b/drivers/net/sfc/Makefile
  index 57aa963ba..359314809 100644
  --- a/drivers/net/sfc/Makefile
  +++ b/drivers/net/sfc/Makefile
  @@ -65,6 +65,7 @@ CFLAGS += -Wbad-function-cast
   CFLAGS_BASE_DRIVER += -Wno-empty-body
   else ifeq ($(CONFIG_RTE_TOOLCHAIN_ICC),y)
   CFLAGS_BASE_DRIVER += -Wno-unused-but-set-variable
  +CFLAGS_sfc_ef10_tx.o += -wd3656
   endif

   #

> +				rte_mempool_put_bulk(bulk[0]->pool,
> +						     (void *)bulk, nb);
> +				nb = 0;
>  			}
> +
> +			bulk[nb++] = m;
>  		} while (++completed != pending);
>  
> +		if (nb != 0)
> +			rte_mempool_put_bulk(bulk[0]->pool, (void *)bulk, nb);
> +
>  		txq->completed = completed;
>  	}

<...>
Stephen Hemminger Sept. 12, 2017, 9:51 p.m. UTC | #2 
On Fri, 8 Sep 2017 15:15:50 +0100
Andrew Rybchenko <arybchenko@solarflare.com> wrote:

> +			txd->mbuf = NULL;
> +			if (m == NULL)
> +				continue;
> +
> +			if ((nb == RTE_DIM(bulk)) ||
> +			    ((nb != 0) && (m->pool != bulk[0]->pool))) {
> +				rte_mempool_put_bulk(bulk[0]->pool,
> +						     (void *)bulk, nb);
> +				nb = 0;
>  			}
> +

Why not add rte_mbuf_free_bulk (inline) to base code, rather than recoding
everywhere?
Andrew Rybchenko Sept. 13, 2017, 6:27 a.m. UTC | #3 
On 09/13/2017 12:51 AM, Stephen Hemminger wrote:
> On Fri, 8 Sep 2017 15:15:50 +0100
> Andrew Rybchenko <arybchenko@solarflare.com> wrote:
>
>> +			txd->mbuf = NULL;
>> +			if (m == NULL)
>> +				continue;
>> +
>> +			if ((nb == RTE_DIM(bulk)) ||
>> +			    ((nb != 0) && (m->pool != bulk[0]->pool))) {
>> +				rte_mempool_put_bulk(bulk[0]->pool,
>> +						     (void *)bulk, nb);
>> +				nb = 0;
>>   			}
>> +
> Why not add rte_mbuf_free_bulk (inline) to base code, rather than recoding
> everywhere?

I'm not 100% sure that I understand the question in a right way, but if 
you're
talking about base driver code, it is not used in native datapath 
implementations
at all (just header files with HW/SW interface definition). In fact 
patches 1 and 2
of the series are slightly different and the difference is proved by 
performance
measurements.
Andrew Rybchenko Sept. 13, 2017, 9:31 a.m. UTC | #4 
On 09/12/2017 09:26 PM, Ferruh Yigit wrote:
> On 9/8/2017 3:15 PM, Andrew Rybchenko wrote:
>> From: Ivan Malov <ivan.malov@oktetlabs.ru>
>>
>> Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
>> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
>> ---
>>   drivers/net/sfc/sfc_ef10_tx.c | 48 ++++++++++++++++++++++++++++++++++++-------
>>   drivers/net/sfc/sfc_tweak.h   |  3 +++
>>   2 files changed, 44 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/net/sfc/sfc_ef10_tx.c b/drivers/net/sfc/sfc_ef10_tx.c
>> index 182fc23..5127a7a 100644
>> --- a/drivers/net/sfc/sfc_ef10_tx.c
>> +++ b/drivers/net/sfc/sfc_ef10_tx.c
>> @@ -158,17 +158,35 @@ struct sfc_ef10_txq {
>>   	pending += sfc_ef10_tx_process_events(txq);
>>   
>>   	if (pending != completed) {
>> +		struct rte_mbuf *bulk[SFC_TX_REAP_BULK_SIZE];
>> +		unsigned int nb = 0;
>> +
>>   		do {
>>   			struct sfc_ef10_tx_sw_desc *txd;
>> +			struct rte_mbuf *m;
>>   
>>   			txd = &txq->sw_ring[completed & ptr_mask];
>> +			if (txd->mbuf == NULL)
>> +				continue;
>>   
>> -			if (txd->mbuf != NULL) {
>> -				rte_pktmbuf_free(txd->mbuf);
>> -				txd->mbuf = NULL;
>> +			m = rte_pktmbuf_prefree_seg(txd->mbuf);
>> +			txd->mbuf = NULL;
>> +			if (m == NULL)
>> +				continue;
>> +
>> +			if ((nb == RTE_DIM(bulk)) ||
>> +			    ((nb != 0) && (m->pool != bulk[0]->pool))) {
> ICC is giving warning [1] here, as far as I can see this is false
> positive but can you please double check in case I am missing something?

Yes, I think it is false positive.

> And unless if you don't see a way to convince icc without effecting
> performance, would you mind updating patch to ignore warning [2] ?

Thanks, done.

>
>
> [1]
> error #3656: variable "bulk" may be used before its value is set
>
> [2]
>    diff --git a/drivers/net/sfc/Makefile b/drivers/net/sfc/Makefile
>    index 57aa963ba..359314809 100644
>    --- a/drivers/net/sfc/Makefile
>    +++ b/drivers/net/sfc/Makefile
>    @@ -65,6 +65,7 @@ CFLAGS += -Wbad-function-cast
>     CFLAGS_BASE_DRIVER += -Wno-empty-body
>     else ifeq ($(CONFIG_RTE_TOOLCHAIN_ICC),y)
>     CFLAGS_BASE_DRIVER += -Wno-unused-but-set-variable
>    +CFLAGS_sfc_ef10_tx.o += -wd3656
>     endif
>
>     #

<...>
diff mbox

Patch

diff --git a/drivers/net/sfc/sfc_ef10_tx.c b/drivers/net/sfc/sfc_ef10_tx.c
index 182fc23..5127a7a 100644
--- a/drivers/net/sfc/sfc_ef10_tx.c
+++ b/drivers/net/sfc/sfc_ef10_tx.c
@@ -158,17 +158,35 @@  struct sfc_ef10_txq {
 	pending += sfc_ef10_tx_process_events(txq);
 
 	if (pending != completed) {
+		struct rte_mbuf *bulk[SFC_TX_REAP_BULK_SIZE];
+		unsigned int nb = 0;
+
 		do {
 			struct sfc_ef10_tx_sw_desc *txd;
+			struct rte_mbuf *m;
 
 			txd = &txq->sw_ring[completed & ptr_mask];
+			if (txd->mbuf == NULL)
+				continue;
 
-			if (txd->mbuf != NULL) {
-				rte_pktmbuf_free(txd->mbuf);
-				txd->mbuf = NULL;
+			m = rte_pktmbuf_prefree_seg(txd->mbuf);
+			txd->mbuf = NULL;
+			if (m == NULL)
+				continue;
+
+			if ((nb == RTE_DIM(bulk)) ||
+			    ((nb != 0) && (m->pool != bulk[0]->pool))) {
+				rte_mempool_put_bulk(bulk[0]->pool,
+						     (void *)bulk, nb);
+				nb = 0;
 			}
+
+			bulk[nb++] = m;
 		} while (++completed != pending);
 
+		if (nb != 0)
+			rte_mempool_put_bulk(bulk[0]->pool, (void *)bulk, nb);
+
 		txq->completed = completed;
 	}
 
@@ -325,6 +343,7 @@  struct sfc_ef10_txq {
 		do {
 			phys_addr_t seg_addr = rte_mbuf_data_dma_addr(m_seg);
 			unsigned int seg_len = rte_pktmbuf_data_len(m_seg);
+			unsigned int id = added & ptr_mask;
 
 			SFC_ASSERT(seg_len <= SFC_EF10_TX_DMA_DESC_LEN_MAX);
 
@@ -332,15 +351,30 @@  struct sfc_ef10_txq {
 
 			sfc_ef10_tx_qdesc_dma_create(seg_addr,
 				seg_len, (pkt_len == 0),
-				&txq->txq_hw_ring[added & ptr_mask]);
+				&txq->txq_hw_ring[id]);
+
+			/*
+			 * rte_pktmbuf_free() is commonly used in DPDK for
+			 * recycling packets - the function checks every
+			 * segment's reference counter and returns the
+			 * buffer to its pool whenever possible;
+			 * nevertheless, freeing mbuf segments one by one
+			 * may entail some performance decline;
+			 * from this point, sfc_efx_tx_reap() does the same job
+			 * on its own and frees buffers in bulks (all mbufs
+			 * within a bulk belong to the same pool);
+			 * from this perspective, individual segment pointers
+			 * must be associated with the corresponding SW
+			 * descriptors independently so that only one loop
+			 * is sufficient on reap to inspect all the buffers
+			 */
+			txq->sw_ring[id].mbuf = m_seg;
+
 			++added;
 
 		} while ((m_seg = m_seg->next) != 0);
 
 		dma_desc_space -= (added - pkt_start);
-
-		/* Assign mbuf to the last used desc */
-		txq->sw_ring[(added - 1) & ptr_mask].mbuf = *pktp;
 	}
 
 	if (likely(added != txq->added)) {
diff --git a/drivers/net/sfc/sfc_tweak.h b/drivers/net/sfc/sfc_tweak.h
index 4ef7fc8..fd2f75c 100644
--- a/drivers/net/sfc/sfc_tweak.h
+++ b/drivers/net/sfc/sfc_tweak.h
@@ -53,4 +53,7 @@ 
 /** Default free threshold follows recommendations from DPDK documentation */
 #define SFC_TX_DEFAULT_FREE_THRESH	32
 
+/** Number of mbufs to be freed in bulk in a single call */
+#define SFC_TX_REAP_BULK_SIZE		32
+
 #endif /* _SFC_TWEAK_H_ */