> On Thu, 10 Oct 2019 01:18:34 +0200 > Lorenzo Bianconi <lore...@kernel.org> wrote: > > > mvneta driver can run on not cache coherent devices so it is > > necessary to sync dma buffers before sending them to the device > > in order to avoid memory corruption. This patch introduce a performance > > penalty and it is necessary to introduce a more sophisticated logic > > in order to avoid dma sync as much as we can > > Report with benchmarks here: > > https://github.com/xdp-project/xdp-project/blob/master/areas/arm64/board_espressobin08_bench_xdp.org
Thx a lot Jesper for detailed report, I will include this info in the commit
log.
Regards,
Lorenzo
>
> We are testing this on an Espressobin board, and do see a huge
> performance cost associated with this DMA-sync. Regardless we still
> want to get this patch merged, to move forward with XDP support for
> this driver.
>
> We promised each-other (on IRC freenode #xdp) that we will follow-up
> with a solution/mitigation, after this patchset is merged. There are
> several ideas, that likely should get separate upstream review.
>
> > Signed-off-by: Lorenzo Bianconi <lore...@kernel.org>
>
> Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
>
> > ---
> > drivers/net/ethernet/marvell/mvneta.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/marvell/mvneta.c
> > b/drivers/net/ethernet/marvell/mvneta.c
> > index 79a6bac0192b..ba4aa9bbc798 100644
> > --- a/drivers/net/ethernet/marvell/mvneta.c
> > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > @@ -1821,6 +1821,7 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
> > struct mvneta_rx_queue *rxq,
> > gfp_t gfp_mask)
> > {
> > + enum dma_data_direction dma_dir;
> > dma_addr_t phys_addr;
> > struct page *page;
> >
> > @@ -1830,6 +1831,9 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
> > return -ENOMEM;
> >
> > phys_addr = page_pool_get_dma_addr(page) + pp->rx_offset_correction;
> > + dma_dir = page_pool_get_dma_dir(rxq->page_pool);
> > + dma_sync_single_for_device(pp->dev->dev.parent, phys_addr,
> > + MVNETA_MAX_RX_BUF_SIZE, dma_dir);
> > mvneta_rx_desc_fill(rx_desc, phys_addr, page, rxq);
> >
> > return 0;
>
>
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
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