* [PATCH] NTB: Address out of DMA descriptor issue with NTB
@ 2016-01-07 23:14 Dave Jiang
2016-01-08 14:57 ` Allen Hubbe
0 siblings, 1 reply; 2+ messages in thread
From: Dave Jiang @ 2016-01-07 23:14 UTC (permalink / raw)
To: allen.hubbe, jdmason; +Cc: linux-ntb
The transport right now does not handle the case where we run out of DMA
descriptors. We just fail when we do not succeed. Adding code to retry for
a bit attempting to use the DMA engine instead of instantly fail to CPU
copy.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
drivers/ntb/ntb_transport.c | 46 ++++++++++++++++++++++++++++++++++++-------
1 file changed, 39 insertions(+), 7 deletions(-)
diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index 60654d5..de95fe9 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -171,12 +171,14 @@ struct ntb_transport_qp {
u64 rx_err_ver;
u64 rx_memcpy;
u64 rx_async;
+ u64 dma_rx_prep_err;
u64 tx_bytes;
u64 tx_pkts;
u64 tx_ring_full;
u64 tx_err_no_buf;
u64 tx_memcpy;
u64 tx_async;
+ u64 dma_tx_prep_err;
};
struct ntb_transport_mw {
@@ -249,6 +251,8 @@ enum {
#define QP_TO_MW(nt, qp) ((qp) % nt->mw_count)
#define NTB_QP_DEF_NUM_ENTRIES 100
#define NTB_LINK_DOWN_TIMEOUT 10
+#define DMA_RETRIES 20
+#define DMA_OUT_RESOURCE_TO 50
static void ntb_transport_rxc_db(unsigned long data);
static const struct ntb_ctx_ops ntb_transport_ops;
@@ -501,6 +505,12 @@ static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
out_offset += snprintf(buf + out_offset, out_count - out_offset,
"free tx - \t%u\n",
ntb_transport_tx_free_entry(qp));
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "DMA tx prep err - \t%llu\n",
+ qp->dma_tx_prep_err);
+ out_offset += snprintf(buf + out_offset, out_count - out_offset,
+ "DMA rx prep err - \t%llu\n",
+ qp->dma_rx_prep_err);
out_offset += snprintf(buf + out_offset, out_count - out_offset,
"\n");
@@ -726,6 +736,8 @@ static void ntb_qp_link_down_reset(struct ntb_transport_qp *qp)
qp->tx_err_no_buf = 0;
qp->tx_memcpy = 0;
qp->tx_async = 0;
+ qp->dma_tx_prep_err = 0;
+ qp->dma_rx_prep_err = 0;
}
static void ntb_qp_link_cleanup(struct ntb_transport_qp *qp)
@@ -1228,6 +1240,7 @@ static void ntb_async_rx(struct ntb_queue_entry *entry, void *offset)
struct dmaengine_unmap_data *unmap;
dma_cookie_t cookie;
void *buf = entry->buf;
+ int retries = 0;
len = entry->len;
@@ -1263,11 +1276,20 @@ static void ntb_async_rx(struct ntb_queue_entry *entry, void *offset)
unmap->from_cnt = 1;
- txd = device->device_prep_dma_memcpy(chan, unmap->addr[1],
- unmap->addr[0], len,
- DMA_PREP_INTERRUPT);
- if (!txd)
+ do {
+ txd = device->device_prep_dma_memcpy(chan, unmap->addr[1],
+ unmap->addr[0], len,
+ DMA_PREP_INTERRUPT);
+ if (!txd) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(DMA_OUT_RESOURCE_TO);
+ }
+ } while (!txd && (++retries < DMA_RETRIES));
+
+ if (!txd) {
+ qp->dma_rx_prep_err++;
goto err_get_unmap;
+ }
txd->callback = ntb_rx_copy_callback;
txd->callback_param = entry;
@@ -1460,6 +1482,7 @@ static void ntb_async_tx(struct ntb_transport_qp *qp,
void __iomem *offset;
size_t len = entry->len;
void *buf = entry->buf;
+ int retries = 0;
offset = qp->tx_mw + qp->tx_max_frame * qp->tx_index;
hdr = offset + qp->tx_max_frame - sizeof(struct ntb_payload_header);
@@ -1494,10 +1517,19 @@ static void ntb_async_tx(struct ntb_transport_qp *qp,
unmap->to_cnt = 1;
- txd = device->device_prep_dma_memcpy(chan, dest, unmap->addr[0], len,
- DMA_PREP_INTERRUPT);
- if (!txd)
+ do {
+ txd = device->device_prep_dma_memcpy(chan, dest, unmap->addr[0],
+ len, DMA_PREP_INTERRUPT);
+ if (!txd) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(DMA_OUT_RESOURCE_TO);
+ }
+ } while (!txd && (++retries < DMA_RETRIES));
+
+ if (!txd) {
+ qp->dma_tx_prep_err++;
goto err_get_unmap;
+ }
txd->callback = ntb_tx_copy_callback;
txd->callback_param = entry;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* RE: [PATCH] NTB: Address out of DMA descriptor issue with NTB
2016-01-07 23:14 [PATCH] NTB: Address out of DMA descriptor issue with NTB Dave Jiang
@ 2016-01-08 14:57 ` Allen Hubbe
0 siblings, 0 replies; 2+ messages in thread
From: Allen Hubbe @ 2016-01-08 14:57 UTC (permalink / raw)
To: 'Dave Jiang', jdmason; +Cc: linux-ntb
From: Dave Jiang <dave.jiang@intel.com>
> The transport right now does not handle the case where we run out of DMA
> descriptors. We just fail when we do not succeed. Adding code to retry
> for
> a bit attempting to use the DMA engine instead of instantly fail to CPU
> copy.
> @@ -1263,11 +1276,20 @@ static void ntb_async_rx(struct ntb_queue_entry
> *entry, void *offset)
> + do {
> + txd = device->device_prep_dma_memcpy(chan, unmap->addr[1],
> + unmap->addr[0], len,
> + DMA_PREP_INTERRUPT);
> + if (!txd) {
> + set_current_state(TASK_INTERRUPTIBLE);
> + schedule_timeout(DMA_OUT_RESOURCE_TO);
> + }
> + } while (!txd && (++retries < DMA_RETRIES));
!txd is tested twice per loop.
How about:
for (retries = 0; retries < DMA_RETRIES; ++retries) {
txd = prep_dma_memcpy();
if (txd)
break;
set_current_state();
schedule_timeout();
}
> @@ -1494,10 +1517,19 @@ static void ntb_async_tx(struct ntb_transport_qp
Also here.
Allen
^ permalink raw reply [flat|nested] 2+ messages in thread
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2016-01-08 14:57 ` Allen Hubbe
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