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mlx4: allow order-0 memory allocations in RX path
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Signed-off-by: Eric Dumazet <edumazet@google.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@google.com>
Cc: Amir Vadai <amirv@mellanox.com>
Acked-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@davem330
Eric Dumazet authored and davem330 committed Jun 25, 2013
1 parent 3bae9db commit 51151a1
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Showing 2 changed files with 95 additions and 86 deletions.
169 changes: 89 additions & 80 deletions drivers/net/ethernet/mellanox/mlx4/en_rx.c
View file
Expand Up @@ -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++) {
Expand All @@ -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;
}
Expand All @@ -104,48 +130,41 @@ 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);
}

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;
Expand All @@ -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;
}
}
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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");
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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++;
}
Expand All @@ -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);
}
}

Expand Down
12 changes: 6 additions & 6 deletions drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
View file
Expand Up @@ -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) */
Expand Down Expand Up @@ -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 {
Expand Down Expand Up @@ -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
Expand Down

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