| Message ID | 1459406190-2334-1-git-send-email-jszhang@marvell.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
Hi, + linux arm kernel On Thu, 31 Mar 2016 14:36:30 +0800 Jisheng Zhang wrote: > The rx descriptors are allocated using dma_alloc_coherent, so prefetch > doesn't really happen at all. This is for RFC, I'm sorry to send it without changing its title -- s/PATCH/RFC. I'm not sure whether there's any benefit to prefetch on space allocated from dma_alloc_coherent. Thanks > > Signed-off-by: Jisheng Zhang <jszhang@marvell.com> > --- > drivers/net/ethernet/marvell/mvneta.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c > index 5880871..6c09a27 100644 > --- a/drivers/net/ethernet/marvell/mvneta.c > +++ b/drivers/net/ethernet/marvell/mvneta.c > @@ -757,7 +757,6 @@ mvneta_rxq_next_desc_get(struct mvneta_rx_queue *rxq) > int rx_desc = rxq->next_desc_to_proc; > > rxq->next_desc_to_proc = MVNETA_QUEUE_NEXT_DESC(rxq, rx_desc); > - prefetch(rxq->descs + rxq->next_desc_to_proc); > return rxq->descs + rx_desc; > } >
Hi all, On Thu, 31 Mar 2016 14:45:37 +0800 Jisheng Zhang wrote: > Hi, > > + linux arm kernel > > On Thu, 31 Mar 2016 14:36:30 +0800 Jisheng Zhang wrote: > > > The rx descriptors are allocated using dma_alloc_coherent, so prefetch > > doesn't really happen at all. > > This is for RFC, I'm sorry to send it without changing its title -- s/PATCH/RFC. > > I'm not sure whether there's any benefit to prefetch on space allocated from > dma_alloc_coherent. After more consideration, I think my patch is wrong. As for coherent platforms, the space allocated from dma_alloc_coherent is cacheable, so prefetch would definitely benefit us. As for noncoherent platforms, the space allocated from dma_alloc_coherent is uncacheable, but prefetch on arm/arm64 is implemented via. pld/prfm, the op would be nop if target address is uncacheable. So let's drop this patch. Thanks, Jisheng > > Thanks > > > > > Signed-off-by: Jisheng Zhang <jszhang@marvell.com> > > --- > > drivers/net/ethernet/marvell/mvneta.c | 1 - > > 1 file changed, 1 deletion(-) > > > > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c > > index 5880871..6c09a27 100644 > > --- a/drivers/net/ethernet/marvell/mvneta.c > > +++ b/drivers/net/ethernet/marvell/mvneta.c > > @@ -757,7 +757,6 @@ mvneta_rxq_next_desc_get(struct mvneta_rx_queue *rxq) > > int rx_desc = rxq->next_desc_to_proc; > > > > rxq->next_desc_to_proc = MVNETA_QUEUE_NEXT_DESC(rxq, rx_desc); > > - prefetch(rxq->descs + rxq->next_desc_to_proc); > > return rxq->descs + rx_desc; > > } > > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index 5880871..6c09a27 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -757,7 +757,6 @@ mvneta_rxq_next_desc_get(struct mvneta_rx_queue *rxq) int rx_desc = rxq->next_desc_to_proc; rxq->next_desc_to_proc = MVNETA_QUEUE_NEXT_DESC(rxq, rx_desc); - prefetch(rxq->descs + rxq->next_desc_to_proc); return rxq->descs + rx_desc; }
The rx descriptors are allocated using dma_alloc_coherent, so prefetch doesn't really happen at all. Signed-off-by: Jisheng Zhang <jszhang@marvell.com> --- drivers/net/ethernet/marvell/mvneta.c | 1 - 1 file changed, 1 deletion(-)