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Date: Tue, 25 Jun 2013 11:53:50 +0300
From: Or Gerlitz <or.gerlitz@...il.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Amir Vadai <amirv@...lanox.com>,
"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
Or Gerlitz <ogerlitz@...lanox.com>,
Yevgeny Petrilin <yevgenyp@...lanox.com>
Subject: Re: [PATCH net-next] mlx4: allow order-0 memory allocations in RX path
On Sun, Jun 23, 2013 at 6:17 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>
> mlx4 exclusively uses order-2 allocations in RX path, which are
> likely to fail under memory pressure.
>
> We therefore drop frames more than needed.
>
> This patch tries order-3, order-2, order-1 and finally order-0
> allocations to keep good performance, yet allow allocations if/when
> memory gets fragmented.
>
> By using larger pages, and avoiding unnecessary get_page()/put_page()
> on compound pages, this patch improves performance as well, lowering
> false sharing on struct page.
>
> Also use GFP_KERNEL allocations in initialization path, as allocating 12
> MB (390 order-3 pages) can easily fail with GFP_ATOMIC.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Amir Vadai <amirv@...lanox.com>
> ---
> drivers/net/ethernet/mellanox/mlx4/en_rx.c | 169 ++++++++---------
> drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 12 -
> 2 files changed, 95 insertions(+), 86 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 9c57581..76997b9 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -43,40 +43,64 @@
>
> #include "mlx4_en.h"
>
> +static int mlx4_alloc_pages(struct mlx4_en_priv *priv,
> + struct mlx4_en_rx_alloc *page_alloc,
> + const struct mlx4_en_frag_info *frag_info,
> + gfp_t _gfp)
> +{
> + int order;
> + struct page *page;
> + dma_addr_t dma;
> +
> + for (order = MLX4_EN_ALLOC_PREFER_ORDER; ;) {
> + gfp_t gfp = _gfp;
> +
> + if (order)
> + gfp |= __GFP_COMP | __GFP_NOWARN;
> + page = alloc_pages(gfp, order);
> + if (likely(page))
> + break;
> + if (--order < 0 ||
> + ((PAGE_SIZE << order) < frag_info->frag_size))
> + return -ENOMEM;
> + }
> + dma = dma_map_page(priv->ddev, page, 0, PAGE_SIZE << order,
> + PCI_DMA_FROMDEVICE);
> + if (dma_mapping_error(priv->ddev, dma)) {
> + put_page(page);
> + return -ENOMEM;
> + }
> + page_alloc->size = PAGE_SIZE << order;
> + page_alloc->page = page;
> + page_alloc->dma = dma;
> + page_alloc->offset = frag_info->frag_align;
> + /* Not doing get_page() for each frag is a big win
> + * on asymetric workloads.
> + */
> + atomic_set(&page->_count, page_alloc->size / frag_info->frag_stride);
> + return 0;
> +}
> +
> static int mlx4_en_alloc_frags(struct mlx4_en_priv *priv,
> struct mlx4_en_rx_desc *rx_desc,
> struct mlx4_en_rx_alloc *frags,
> - struct mlx4_en_rx_alloc *ring_alloc)
> + struct mlx4_en_rx_alloc *ring_alloc,
> + gfp_t gfp)
> {
> struct mlx4_en_rx_alloc page_alloc[MLX4_EN_MAX_RX_FRAGS];
> - struct mlx4_en_frag_info *frag_info;
> + const struct mlx4_en_frag_info *frag_info;
> struct page *page;
> dma_addr_t dma;
> int i;
>
> for (i = 0; i < priv->num_frags; i++) {
> frag_info = &priv->frag_info[i];
> - if (ring_alloc[i].offset == frag_info->last_offset) {
> - page = alloc_pages(GFP_ATOMIC | __GFP_COMP,
> - MLX4_EN_ALLOC_ORDER);
> - if (!page)
> - goto out;
> - dma = dma_map_page(priv->ddev, page, 0,
> - MLX4_EN_ALLOC_SIZE, PCI_DMA_FROMDEVICE);
> - if (dma_mapping_error(priv->ddev, dma)) {
> - put_page(page);
> - goto out;
> - }
> - page_alloc[i].page = page;
> - page_alloc[i].dma = dma;
> - page_alloc[i].offset = frag_info->frag_align;
> - } else {
> - page_alloc[i].page = ring_alloc[i].page;
> - get_page(ring_alloc[i].page);
> - page_alloc[i].dma = ring_alloc[i].dma;
> - page_alloc[i].offset = ring_alloc[i].offset +
> - frag_info->frag_stride;
> - }
> + page_alloc[i] = ring_alloc[i];
> + page_alloc[i].offset += frag_info->frag_stride;
> + if (page_alloc[i].offset + frag_info->frag_stride <= ring_alloc[i].size)
> + continue;
> + if (mlx4_alloc_pages(priv, &page_alloc[i], frag_info, gfp))
> + goto out;
> }
>
> for (i = 0; i < priv->num_frags; i++) {
> @@ -88,14 +112,16 @@ static int mlx4_en_alloc_frags(struct mlx4_en_priv *priv,
>
> return 0;
>
> -
> out:
> while (i--) {
> frag_info = &priv->frag_info[i];
> - if (ring_alloc[i].offset == frag_info->last_offset)
> + if (page_alloc[i].page != ring_alloc[i].page) {
> dma_unmap_page(priv->ddev, page_alloc[i].dma,
> - MLX4_EN_ALLOC_SIZE, PCI_DMA_FROMDEVICE);
> - put_page(page_alloc[i].page);
> + page_alloc[i].size, PCI_DMA_FROMDEVICE);
> + page = page_alloc[i].page;
> + atomic_set(&page->_count, 1);
> + put_page(page);
> + }
> }
> return -ENOMEM;
> }
> @@ -104,12 +130,12 @@ static void mlx4_en_free_frag(struct mlx4_en_priv *priv,
> struct mlx4_en_rx_alloc *frags,
> int i)
> {
> - struct mlx4_en_frag_info *frag_info = &priv->frag_info[i];
> + const struct mlx4_en_frag_info *frag_info = &priv->frag_info[i];
>
> - if (frags[i].offset == frag_info->last_offset) {
> - dma_unmap_page(priv->ddev, frags[i].dma, MLX4_EN_ALLOC_SIZE,
> + if (frags[i].offset + frag_info->frag_stride > frags[i].size)
> + dma_unmap_page(priv->ddev, frags[i].dma, frags[i].size,
> PCI_DMA_FROMDEVICE);
> - }
> +
> if (frags[i].page)
> put_page(frags[i].page);
> }
> @@ -117,35 +143,28 @@ static void mlx4_en_free_frag(struct mlx4_en_priv *priv,
> static int mlx4_en_init_allocator(struct mlx4_en_priv *priv,
> struct mlx4_en_rx_ring *ring)
> {
> - struct mlx4_en_rx_alloc *page_alloc;
> int i;
> + struct mlx4_en_rx_alloc *page_alloc;
>
> for (i = 0; i < priv->num_frags; i++) {
> - page_alloc = &ring->page_alloc[i];
> - page_alloc->page = alloc_pages(GFP_ATOMIC | __GFP_COMP,
> - MLX4_EN_ALLOC_ORDER);
> - if (!page_alloc->page)
> - goto out;
> + const struct mlx4_en_frag_info *frag_info = &priv->frag_info[i];
>
> - page_alloc->dma = dma_map_page(priv->ddev, page_alloc->page, 0,
> - MLX4_EN_ALLOC_SIZE, PCI_DMA_FROMDEVICE);
> - if (dma_mapping_error(priv->ddev, page_alloc->dma)) {
> - put_page(page_alloc->page);
> - page_alloc->page = NULL;
> + if (mlx4_alloc_pages(priv, &ring->page_alloc[i],
> + frag_info, GFP_KERNEL))
> goto out;
> - }
> - page_alloc->offset = priv->frag_info[i].frag_align;
> - en_dbg(DRV, priv, "Initialized allocator:%d with page:%p\n",
> - i, page_alloc->page);
> }
> return 0;
>
> out:
> while (i--) {
> + struct page *page;
> +
> page_alloc = &ring->page_alloc[i];
> dma_unmap_page(priv->ddev, page_alloc->dma,
> - MLX4_EN_ALLOC_SIZE, PCI_DMA_FROMDEVICE);
> - put_page(page_alloc->page);
> + page_alloc->size, PCI_DMA_FROMDEVICE);
> + page = page_alloc->page;
> + atomic_set(&page->_count, 1);
> + put_page(page);
> page_alloc->page = NULL;
> }
> return -ENOMEM;
> @@ -158,13 +177,18 @@ static void mlx4_en_destroy_allocator(struct mlx4_en_priv *priv,
> int i;
>
> for (i = 0; i < priv->num_frags; i++) {
> + const struct mlx4_en_frag_info *frag_info = &priv->frag_info[i];
> +
> page_alloc = &ring->page_alloc[i];
> en_dbg(DRV, priv, "Freeing allocator:%d count:%d\n",
> i, page_count(page_alloc->page));
>
> dma_unmap_page(priv->ddev, page_alloc->dma,
> - MLX4_EN_ALLOC_SIZE, PCI_DMA_FROMDEVICE);
> - put_page(page_alloc->page);
> + page_alloc->size, PCI_DMA_FROMDEVICE);
> + while (page_alloc->offset + frag_info->frag_stride < page_alloc->size) {
> + put_page(page_alloc->page);
> + page_alloc->offset += frag_info->frag_stride;
> + }
> page_alloc->page = NULL;
> }
> }
> @@ -195,13 +219,14 @@ static void mlx4_en_init_rx_desc(struct mlx4_en_priv *priv,
> }
>
> static int mlx4_en_prepare_rx_desc(struct mlx4_en_priv *priv,
> - struct mlx4_en_rx_ring *ring, int index)
> + struct mlx4_en_rx_ring *ring, int index,
> + gfp_t gfp)
> {
> struct mlx4_en_rx_desc *rx_desc = ring->buf + (index * ring->stride);
> struct mlx4_en_rx_alloc *frags = ring->rx_info +
> (index << priv->log_rx_info);
>
> - return mlx4_en_alloc_frags(priv, rx_desc, frags, ring->page_alloc);
> + return mlx4_en_alloc_frags(priv, rx_desc, frags, ring->page_alloc, gfp);
> }
>
> static inline void mlx4_en_update_rx_prod_db(struct mlx4_en_rx_ring *ring)
> @@ -235,7 +260,8 @@ static int mlx4_en_fill_rx_buffers(struct mlx4_en_priv *priv)
> ring = &priv->rx_ring[ring_ind];
>
> if (mlx4_en_prepare_rx_desc(priv, ring,
> - ring->actual_size)) {
> + ring->actual_size,
> + GFP_KERNEL)) {
> if (ring->actual_size < MLX4_EN_MIN_RX_SIZE) {
> en_err(priv, "Failed to allocate "
> "enough rx buffers\n");
> @@ -450,11 +476,11 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
> DMA_FROM_DEVICE);
>
> /* Save page reference in skb */
> - get_page(frags[nr].page);
> __skb_frag_set_page(&skb_frags_rx[nr], frags[nr].page);
> skb_frag_size_set(&skb_frags_rx[nr], frag_info->frag_size);
> skb_frags_rx[nr].page_offset = frags[nr].offset;
> skb->truesize += frag_info->frag_stride;
> + frags[nr].page = NULL;
> }
> /* Adjust size of last fragment to match actual length */
> if (nr > 0)
> @@ -547,7 +573,7 @@ static void mlx4_en_refill_rx_buffers(struct mlx4_en_priv *priv,
> int index = ring->prod & ring->size_mask;
>
> while ((u32) (ring->prod - ring->cons) < ring->actual_size) {
> - if (mlx4_en_prepare_rx_desc(priv, ring, index))
> + if (mlx4_en_prepare_rx_desc(priv, ring, index, GFP_ATOMIC))
> break;
> ring->prod++;
> index = ring->prod & ring->size_mask;
> @@ -805,21 +831,7 @@ int mlx4_en_poll_rx_cq(struct napi_struct *napi, int budget)
> return done;
> }
>
> -
> -/* Calculate the last offset position that accommodates a full fragment
> - * (assuming fagment size = stride-align) */
> -static int mlx4_en_last_alloc_offset(struct mlx4_en_priv *priv, u16 stride, u16 align)
> -{
> - u16 res = MLX4_EN_ALLOC_SIZE % stride;
> - u16 offset = MLX4_EN_ALLOC_SIZE - stride - res + align;
> -
> - en_dbg(DRV, priv, "Calculated last offset for stride:%d align:%d "
> - "res:%d offset:%d\n", stride, align, res, offset);
> - return offset;
> -}
> -
> -
> -static int frag_sizes[] = {
> +static const int frag_sizes[] = {
> FRAG_SZ0,
> FRAG_SZ1,
> FRAG_SZ2,
> @@ -847,9 +859,6 @@ void mlx4_en_calc_rx_buf(struct net_device *dev)
> priv->frag_info[i].frag_stride =
> ALIGN(frag_sizes[i], SMP_CACHE_BYTES);
> }
> - priv->frag_info[i].last_offset = mlx4_en_last_alloc_offset(
> - priv, priv->frag_info[i].frag_stride,
> - priv->frag_info[i].frag_align);
> buf_size += priv->frag_info[i].frag_size;
> i++;
> }
> @@ -861,13 +870,13 @@ void mlx4_en_calc_rx_buf(struct net_device *dev)
> en_dbg(DRV, priv, "Rx buffer scatter-list (effective-mtu:%d "
> "num_frags:%d):\n", eff_mtu, priv->num_frags);
> for (i = 0; i < priv->num_frags; i++) {
> - en_dbg(DRV, priv, " frag:%d - size:%d prefix:%d align:%d "
> - "stride:%d last_offset:%d\n", i,
> - priv->frag_info[i].frag_size,
> - priv->frag_info[i].frag_prefix_size,
> - priv->frag_info[i].frag_align,
> - priv->frag_info[i].frag_stride,
> - priv->frag_info[i].last_offset);
> + en_err(priv,
> + " frag:%d - size:%d prefix:%d align:%d stride:%d\n",
> + i,
> + priv->frag_info[i].frag_size,
> + priv->frag_info[i].frag_prefix_size,
> + priv->frag_info[i].frag_align,
> + priv->frag_info[i].frag_stride);
> }
> }
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> index 57192a8..35fb60e 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> @@ -96,7 +96,8 @@
>
> /* Use the maximum between 16384 and a single page */
> #define MLX4_EN_ALLOC_SIZE PAGE_ALIGN(16384)
> -#define MLX4_EN_ALLOC_ORDER get_order(MLX4_EN_ALLOC_SIZE)
> +
> +#define MLX4_EN_ALLOC_PREFER_ORDER PAGE_ALLOC_COSTLY_ORDER
>
> /* Receive fragment sizes; we use at most 3 fragments (for 9600 byte MTU
> * and 4K allocations) */
> @@ -234,9 +235,10 @@ struct mlx4_en_tx_desc {
> #define MLX4_EN_CX3_HIGH_ID 0x1005
>
> struct mlx4_en_rx_alloc {
> - struct page *page;
> - dma_addr_t dma;
> - u16 offset;
> + struct page *page;
> + dma_addr_t dma;
> + u32 offset;
> + u32 size;
> };
>
> struct mlx4_en_tx_ring {
> @@ -439,8 +441,6 @@ struct mlx4_en_frag_info {
> u16 frag_prefix_size;
> u16 frag_stride;
> u16 frag_align;
> - u16 last_offset;
> -
> };
>
> #ifdef CONFIG_MLX4_EN_DCB
Amir is OOO and I am covering for him, so:
Acked-by: Or Gerlitz <ogerlitz@...lanox.com>
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