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Date: Thu, 31 Mar 2016 15:15:01 +0800 From: Jisheng Zhang <jszhang@...vell.com> To: <thomas.petazzoni@...e-electrons.com>, <gregory.clement@...e-electrons.com>, <davem@...emloft.net> CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH] net: mvneta: remove useless RX descriptor prefetch 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@...vell.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@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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