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sfc: Simplify TSO header buffer allocation 

TSO header buffers contain a control structure immediately followed by
the packet headers, and are kept on a free list when not in use.  This
complicates buffer management and tends to result in cache read misses
when we recycle such buffers (particularly if DMA-coherent memory
requires caches to be disabled).

Replace the free list with a simple mapping by descriptor index.  We
know that there is always a payload descriptor between any two
descriptors with TSO header buffers, so we can allocate only one
such buffer for each two descriptors.

While we're at it, use a standard error code for allocation failure,
not -1.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
This commit is contained in:
Ben Hutchings 2012-05-17 18:40:54 +01:00
parent 14bf718fb9
commit f7251a9ce9
3 changed files with 116 additions and 222 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/net/ethernet/sfc/net_driver.h
View File

@ -94,7 +94,8 @@ struct efx_special_buffer {
* struct efx_tx_buffer - buffer state for a TX descriptor
* @skb: When @flags & %EFX_TX_BUF_SKB, the associated socket buffer to be
* freed when descriptor completes
* @tsoh: When @flags & %EFX_TX_BUF_TSOH, the associated TSO header structure.
* @heap_buf: When @flags & %EFX_TX_BUF_HEAP, the associated heap buffer to be
* freed when descriptor completes.
* @dma_addr: DMA address of the fragment.
* @flags: Flags for allocation and DMA mapping type
* @len: Length of this fragment.
@ -104,7 +105,7 @@ struct efx_special_buffer {
struct efx_tx_buffer {
union {
const struct sk_buff *skb;
struct efx_tso_header *tsoh;
void *heap_buf;
};
dma_addr_t dma_addr;
unsigned short flags;
@ -113,7 +114,7 @@ struct efx_tx_buffer {
};
#define EFX_TX_BUF_CONT 1 /* not last descriptor of packet */
#define EFX_TX_BUF_SKB 2 /* buffer is last part of skb */
#define EFX_TX_BUF_TSOH 4 /* buffer is TSO header */
#define EFX_TX_BUF_HEAP 4 /* buffer was allocated with kmalloc() */
#define EFX_TX_BUF_MAP_SINGLE 8 /* buffer was mapped with dma_map_single() */
/**
@ -134,6 +135,7 @@ struct efx_tx_buffer {
* @channel: The associated channel
* @core_txq: The networking core TX queue structure
* @buffer: The software buffer ring
* @tsoh_page: Array of pages of TSO header buffers
* @txd: The hardware descriptor ring
* @ptr_mask: The size of the ring minus 1.
* @initialised: Has hardware queue been initialised?
@ -157,9 +159,6 @@ struct efx_tx_buffer {
* variable indicates that the queue is full. This is to
* avoid cache-line ping-pong between the xmit path and the
* completion path.
* @tso_headers_free: A list of TSO headers allocated for this TX queue
* that are not in use, and so available for new TSO sends. The list
* is protected by the TX queue lock.
* @tso_bursts: Number of times TSO xmit invoked by kernel
* @tso_long_headers: Number of packets with headers too long for standard
* blocks
@ -176,6 +175,7 @@ struct efx_tx_queue {
struct efx_channel *channel;
struct netdev_queue *core_txq;
struct efx_tx_buffer *buffer;
struct efx_buffer *tsoh_page;
struct efx_special_buffer txd;
unsigned int ptr_mask;
bool initialised;
@ -188,7 +188,6 @@ struct efx_tx_queue {
unsigned int insert_count ____cacheline_aligned_in_smp;
unsigned int write_count;
unsigned int old_read_count;
struct efx_tso_header *tso_headers_free;
unsigned int tso_bursts;
unsigned int tso_long_headers;
unsigned int tso_packets;

2
drivers/net/ethernet/sfc/nic.c
View File

@ -298,7 +298,7 @@ efx_free_special_buffer(struct efx_nic *efx, struct efx_special_buffer *buffer)
/**************************************************************************
*
* Generic buffer handling
* These buffers are used for interrupt status and MAC stats
* These buffers are used for interrupt status, MAC stats, etc.
*
**************************************************************************/

323
drivers/net/ethernet/sfc/tx.c
View File

@ -47,51 +47,16 @@ static void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
netif_vdbg(tx_queue->efx, tx_done, tx_queue->efx->net_dev,
"TX queue %d transmission id %x complete\n",
tx_queue->queue, tx_queue->read_count);
} else if (buffer->flags & EFX_TX_BUF_HEAP) {
kfree(buffer->heap_buf);
}
buffer->flags &= EFX_TX_BUF_TSOH;
buffer->len = 0;
buffer->flags = 0;
}
/**
* struct efx_tso_header - a DMA mapped buffer for packet headers
* @next: Linked list of free ones.
* The list is protected by the TX queue lock.
* @dma_unmap_len: Length to unmap for an oversize buffer, or 0.
* @dma_addr: The DMA address of the header below.
*
* This controls the memory used for a TSO header. Use TSOH_DATA()
* to find the packet header data. Use TSOH_SIZE() to calculate the
* total size required for a given packet header length. TSO headers
* in the free list are exactly %TSOH_STD_SIZE bytes in size.
*/
struct efx_tso_header {
union {
struct efx_tso_header *next;
size_t unmap_len;
};
dma_addr_t dma_addr;
};
static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue,
struct sk_buff *skb);
static void efx_fini_tso(struct efx_tx_queue *tx_queue);
static void efx_tsoh_heap_free(struct efx_tx_queue *tx_queue,
struct efx_tso_header *tsoh);
static void efx_tsoh_free(struct efx_tx_queue *tx_queue,
struct efx_tx_buffer *buffer)
{
if (buffer->flags & EFX_TX_BUF_TSOH) {
if (likely(!buffer->tsoh->unmap_len)) {
buffer->tsoh->next = tx_queue->tso_headers_free;
tx_queue->tso_headers_free = buffer->tsoh;
} else {
efx_tsoh_heap_free(tx_queue, buffer->tsoh);
}
buffer->flags &= ~EFX_TX_BUF_TSOH;
}
}
static inline unsigned
efx_max_tx_len(struct efx_nic *efx, dma_addr_t dma_addr)
@ -245,7 +210,6 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
do {
insert_ptr = tx_queue->insert_count & tx_queue->ptr_mask;
buffer = &tx_queue->buffer[insert_ptr];
efx_tsoh_free(tx_queue, buffer);
EFX_BUG_ON_PARANOID(buffer->flags);
EFX_BUG_ON_PARANOID(buffer->len);
EFX_BUG_ON_PARANOID(buffer->unmap_len);
@ -309,7 +273,6 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
insert_ptr = tx_queue->insert_count & tx_queue->ptr_mask;
buffer = &tx_queue->buffer[insert_ptr];
efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);
buffer->len = 0;
}
/* Free the fragment we were mid-way through pushing */
@ -352,7 +315,6 @@ static void efx_dequeue_buffers(struct efx_tx_queue *tx_queue,
}
efx_dequeue_buffer(tx_queue, buffer, pkts_compl, bytes_compl);
buffer->len = 0;
++tx_queue->read_count;
read_ptr = tx_queue->read_count & tx_queue->ptr_mask;
@ -495,6 +457,21 @@ void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
}
}
/* Size of page-based TSO header buffers. Larger blocks must be
* allocated from the heap.
*/
#define TSOH_STD_SIZE 128
#define TSOH_PER_PAGE (PAGE_SIZE / TSOH_STD_SIZE)
/* At most half the descriptors in the queue at any time will refer to
* a TSO header buffer, since they must always be followed by a
* payload descriptor referring to an skb.
*/
static unsigned int efx_tsoh_page_count(struct efx_tx_queue *tx_queue)
{
return DIV_ROUND_UP(tx_queue->ptr_mask + 1, 2 * TSOH_PER_PAGE);
}
int efx_probe_tx_queue(struct efx_tx_queue *tx_queue)
{
struct efx_nic *efx = tx_queue->efx;
@ -516,14 +493,27 @@ int efx_probe_tx_queue(struct efx_tx_queue *tx_queue)
if (!tx_queue->buffer)
return -ENOMEM;
if (tx_queue->queue & EFX_TXQ_TYPE_OFFLOAD) {
tx_queue->tsoh_page =
kcalloc(efx_tsoh_page_count(tx_queue),
sizeof(tx_queue->tsoh_page[0]), GFP_KERNEL);
if (!tx_queue->tsoh_page) {
rc = -ENOMEM;
goto fail1;
}
}
/* Allocate hardware ring */
rc = efx_nic_probe_tx(tx_queue);
if (rc)
goto fail;
goto fail2;
return 0;
fail:
fail2:
kfree(tx_queue->tsoh_page);
tx_queue->tsoh_page = NULL;
fail1:
kfree(tx_queue->buffer);
tx_queue->buffer = NULL;
return rc;
@ -559,7 +549,6 @@ void efx_release_tx_buffers(struct efx_tx_queue *tx_queue)
unsigned int pkts_compl = 0, bytes_compl = 0;
buffer = &tx_queue->buffer[tx_queue->read_count & tx_queue->ptr_mask];
efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);
buffer->len = 0;
++tx_queue->read_count;
}
@ -580,13 +569,12 @@ void efx_fini_tx_queue(struct efx_tx_queue *tx_queue)
efx_nic_fini_tx(tx_queue);
efx_release_tx_buffers(tx_queue);
/* Free up TSO header cache */
efx_fini_tso(tx_queue);
}
void efx_remove_tx_queue(struct efx_tx_queue *tx_queue)
{
int i;
if (!tx_queue->buffer)
return;
@ -594,6 +582,14 @@ void efx_remove_tx_queue(struct efx_tx_queue *tx_queue)
"destroying TX queue %d\n", tx_queue->queue);
efx_nic_remove_tx(tx_queue);
if (tx_queue->tsoh_page) {
for (i = 0; i < efx_tsoh_page_count(tx_queue); i++)
efx_nic_free_buffer(tx_queue->efx,
&tx_queue->tsoh_page[i]);
kfree(tx_queue->tsoh_page);
tx_queue->tsoh_page = NULL;
}
kfree(tx_queue->buffer);
tx_queue->buffer = NULL;
}
@ -616,17 +612,6 @@ void efx_remove_tx_queue(struct efx_tx_queue *tx_queue)
#define TSOH_OFFSET NET_IP_ALIGN
#endif
#define TSOH_BUFFER(tsoh) ((u8 *)(tsoh + 1) + TSOH_OFFSET)
/* Total size of struct efx_tso_header, buffer and padding */
#define TSOH_SIZE(hdr_len) \
(sizeof(struct efx_tso_header) + TSOH_OFFSET + hdr_len)
/* Size of blocks on free list. Larger blocks must be allocated from
* the heap.
*/
#define TSOH_STD_SIZE 128
#define PTR_DIFF(p1, p2) ((u8 *)(p1) - (u8 *)(p2))
#define ETH_HDR_LEN(skb) (skb_network_header(skb) - (skb)->data)
#define SKB_TCP_OFF(skb) PTR_DIFF(tcp_hdr(skb), (skb)->data)
@ -699,91 +684,43 @@ static __be16 efx_tso_check_protocol(struct sk_buff *skb)
return protocol;
}
/*
* Allocate a page worth of efx_tso_header structures, and string them
* into the tx_queue->tso_headers_free linked list. Return 0 or -ENOMEM.
*/
static int efx_tsoh_block_alloc(struct efx_tx_queue *tx_queue)
static u8 *efx_tsoh_get_buffer(struct efx_tx_queue *tx_queue,
struct efx_tx_buffer *buffer, unsigned int len)
{
struct device *dma_dev = &tx_queue->efx->pci_dev->dev;
struct efx_tso_header *tsoh;
dma_addr_t dma_addr;
u8 *base_kva, *kva;
u8 *result;
base_kva = dma_alloc_coherent(dma_dev, PAGE_SIZE, &dma_addr, GFP_ATOMIC);
if (base_kva == NULL) {
netif_err(tx_queue->efx, tx_err, tx_queue->efx->net_dev,
"Unable to allocate page for TSO headers\n");
return -ENOMEM;
EFX_BUG_ON_PARANOID(buffer->len);
EFX_BUG_ON_PARANOID(buffer->flags);
EFX_BUG_ON_PARANOID(buffer->unmap_len);
if (likely(len <= TSOH_STD_SIZE - TSOH_OFFSET)) {
unsigned index =
(tx_queue->insert_count & tx_queue->ptr_mask) / 2;
struct efx_buffer *page_buf =
&tx_queue->tsoh_page[index / TSOH_PER_PAGE];
unsigned offset =
TSOH_STD_SIZE * (index % TSOH_PER_PAGE) + TSOH_OFFSET;
if (unlikely(!page_buf->addr) &&
efx_nic_alloc_buffer(tx_queue->efx, page_buf, PAGE_SIZE))
return NULL;
result = (u8 *)page_buf->addr + offset;
buffer->dma_addr = page_buf->dma_addr + offset;
buffer->flags = EFX_TX_BUF_CONT;
} else {
tx_queue->tso_long_headers++;
buffer->heap_buf = kmalloc(TSOH_OFFSET + len, GFP_ATOMIC);
if (unlikely(!buffer->heap_buf))
return NULL;
result = (u8 *)buffer->heap_buf + TSOH_OFFSET;
buffer->flags = EFX_TX_BUF_CONT | EFX_TX_BUF_HEAP;
}
/* dma_alloc_coherent() allocates pages. */
EFX_BUG_ON_PARANOID(dma_addr & (PAGE_SIZE - 1u));
buffer->len = len;
for (kva = base_kva; kva < base_kva + PAGE_SIZE; kva += TSOH_STD_SIZE) {
tsoh = (struct efx_tso_header *)kva;
tsoh->dma_addr = dma_addr + (TSOH_BUFFER(tsoh) - base_kva);
tsoh->next = tx_queue->tso_headers_free;
tx_queue->tso_headers_free = tsoh;
}
return 0;
}
/* Free up a TSO header, and all others in the same page. */
static void efx_tsoh_block_free(struct efx_tx_queue *tx_queue,
struct efx_tso_header *tsoh,
struct device *dma_dev)
{
struct efx_tso_header **p;
unsigned long base_kva;
dma_addr_t base_dma;
base_kva = (unsigned long)tsoh & PAGE_MASK;
base_dma = tsoh->dma_addr & PAGE_MASK;
p = &tx_queue->tso_headers_free;
while (*p != NULL) {
if (((unsigned long)*p & PAGE_MASK) == base_kva)
*p = (*p)->next;
else
p = &(*p)->next;
}
dma_free_coherent(dma_dev, PAGE_SIZE, (void *)base_kva, base_dma);
}
static struct efx_tso_header *
efx_tsoh_heap_alloc(struct efx_tx_queue *tx_queue, size_t header_len)
{
struct efx_tso_header *tsoh;
tsoh = kmalloc(TSOH_SIZE(header_len), GFP_ATOMIC | GFP_DMA);
if (unlikely(!tsoh))
return NULL;
tsoh->dma_addr = dma_map_single(&tx_queue->efx->pci_dev->dev,
TSOH_BUFFER(tsoh), header_len,
DMA_TO_DEVICE);
if (unlikely(dma_mapping_error(&tx_queue->efx->pci_dev->dev,
tsoh->dma_addr))) {
kfree(tsoh);
return NULL;
}
tsoh->unmap_len = header_len;
return tsoh;
}
static void
efx_tsoh_heap_free(struct efx_tx_queue *tx_queue, struct efx_tso_header *tsoh)
{
dma_unmap_single(&tx_queue->efx->pci_dev->dev,
tsoh->dma_addr, tsoh->unmap_len,
DMA_TO_DEVICE);
kfree(tsoh);
return result;
}
/**
@ -814,7 +751,6 @@ static void efx_tx_queue_insert(struct efx_tx_queue *tx_queue,
tx_queue->read_count >=
efx->txq_entries);
efx_tsoh_free(tx_queue, buffer);
EFX_BUG_ON_PARANOID(buffer->len);
EFX_BUG_ON_PARANOID(buffer->unmap_len);
EFX_BUG_ON_PARANOID(buffer->flags);
@ -846,53 +782,42 @@ static void efx_tx_queue_insert(struct efx_tx_queue *tx_queue,
* a single fragment, and we know it doesn't cross a page boundary. It
* also allows us to not worry about end-of-packet etc.
*/
static void efx_tso_put_header(struct efx_tx_queue *tx_queue,
struct efx_tso_header *tsoh, unsigned len)
static int efx_tso_put_header(struct efx_tx_queue *tx_queue,
struct efx_tx_buffer *buffer, u8 *header)
{
struct efx_tx_buffer *buffer;
buffer = &tx_queue->buffer[tx_queue->insert_count & tx_queue->ptr_mask];
efx_tsoh_free(tx_queue, buffer);
EFX_BUG_ON_PARANOID(buffer->len);
EFX_BUG_ON_PARANOID(buffer->unmap_len);
EFX_BUG_ON_PARANOID(buffer->flags);
buffer->len = len;
buffer->dma_addr = tsoh->dma_addr;
buffer->tsoh = tsoh;
buffer->flags = EFX_TX_BUF_TSOH | EFX_TX_BUF_CONT;
if (unlikely(buffer->flags & EFX_TX_BUF_HEAP)) {
buffer->dma_addr = dma_map_single(&tx_queue->efx->pci_dev->dev,
header, buffer->len,
DMA_TO_DEVICE);
if (unlikely(dma_mapping_error(&tx_queue->efx->pci_dev->dev,
buffer->dma_addr))) {
kfree(buffer->heap_buf);
buffer->len = 0;
buffer->flags = 0;
return -ENOMEM;
}
buffer->unmap_len = buffer->len;
buffer->flags |= EFX_TX_BUF_MAP_SINGLE;
}
++tx_queue->insert_count;
return 0;
}
/* Remove descriptors put into a tx_queue. */
/* Remove buffers put into a tx_queue. None of the buffers must have
* an skb attached.
*/
static void efx_enqueue_unwind(struct efx_tx_queue *tx_queue)
{
struct efx_tx_buffer *buffer;
dma_addr_t unmap_addr;
/* Work backwards until we hit the original insert pointer value */
while (tx_queue->insert_count != tx_queue->write_count) {
--tx_queue->insert_count;
buffer = &tx_queue->buffer[tx_queue->insert_count &
tx_queue->ptr_mask];
efx_tsoh_free(tx_queue, buffer);
EFX_BUG_ON_PARANOID(buffer->flags & EFX_TX_BUF_SKB);
if (buffer->unmap_len) {
unmap_addr = (buffer->dma_addr + buffer->len -
buffer->unmap_len);
if (buffer->flags & EFX_TX_BUF_MAP_SINGLE)
dma_unmap_single(&tx_queue->efx->pci_dev->dev,
unmap_addr, buffer->unmap_len,
DMA_TO_DEVICE);
else
dma_unmap_page(&tx_queue->efx->pci_dev->dev,
unmap_addr, buffer->unmap_len,
DMA_TO_DEVICE);
buffer->unmap_len = 0;
}
buffer->len = 0;
buffer->flags = 0;
efx_dequeue_buffer(tx_queue, buffer, NULL, NULL);
}
}
@ -1014,35 +939,24 @@ static void tso_fill_packet_with_fragment(struct efx_tx_queue *tx_queue,
* @st: TSO state
*
* Generate a new header and prepare for the new packet. Return 0 on
* success, or -1 if failed to alloc header.
* success, or -%ENOMEM if failed to alloc header.
*/
static int tso_start_new_packet(struct efx_tx_queue *tx_queue,
const struct sk_buff *skb,
struct tso_state *st)
{
struct efx_tso_header *tsoh;
struct efx_tx_buffer *buffer =
&tx_queue->buffer[tx_queue->insert_count & tx_queue->ptr_mask];
struct tcphdr *tsoh_th;
unsigned ip_length;
u8 *header;
int rc;
/* Allocate a DMA-mapped header buffer. */
if (likely(TSOH_SIZE(st->header_len) <= TSOH_STD_SIZE)) {
if (tx_queue->tso_headers_free == NULL) {
if (efx_tsoh_block_alloc(tx_queue))
return -1;
}
EFX_BUG_ON_PARANOID(!tx_queue->tso_headers_free);
tsoh = tx_queue->tso_headers_free;
tx_queue->tso_headers_free = tsoh->next;
tsoh->unmap_len = 0;
} else {
tx_queue->tso_long_headers++;
tsoh = efx_tsoh_heap_alloc(tx_queue, st->header_len);
if (unlikely(!tsoh))
return -1;
}
/* Allocate and insert a DMA-mapped header buffer. */
header = efx_tsoh_get_buffer(tx_queue, buffer, st->header_len);
if (!header)
return -ENOMEM;
header = TSOH_BUFFER(tsoh);
tsoh_th = (struct tcphdr *)(header + SKB_TCP_OFF(skb));
/* Copy and update the headers. */
@ -1078,12 +992,13 @@ static int tso_start_new_packet(struct efx_tx_queue *tx_queue,
tsoh_iph->payload_len = htons(ip_length - sizeof(*tsoh_iph));
}
rc = efx_tso_put_header(tx_queue, buffer, header);
if (unlikely(rc))
return rc;
st->packet_space = skb_shinfo(skb)->gso_size;
++tx_queue->tso_packets;
/* Form a descriptor for this header. */
efx_tso_put_header(tx_queue, tsoh, st->header_len);
return 0;
}
@ -1182,23 +1097,3 @@ static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue,
efx_enqueue_unwind(tx_queue);
return NETDEV_TX_OK;
}
/*
* Free up all TSO datastructures associated with tx_queue. This
* routine should be called only once the tx_queue is both empty and
* will no longer be used.
*/
static void efx_fini_tso(struct efx_tx_queue *tx_queue)
{
unsigned i;
if (tx_queue->buffer) {
for (i = 0; i <= tx_queue->ptr_mask; ++i)
efx_tsoh_free(tx_queue, &tx_queue->buffer[i]);
}
while (tx_queue->tso_headers_free != NULL)
efx_tsoh_block_free(tx_queue, tx_queue->tso_headers_free,
&tx_queue->efx->pci_dev->dev);
}