On 8/8/19 11:22 AM, Thierry Herbelot wrote:
From: Olivier Matz <olivier.m...@6wind.com>
The API comment of rte_eth_tx_descriptor_status() was incorrect. The
reference descriptor (when offset = 0) is not where the next packet
will be sent, but where the latest packet has been enqueued.
Fixes: 52f5cdd2e897 ("ethdev: add descriptor status API")
Cc: sta...@dpdk.org
Signed-off-by: Olivier Matz <olivier.m...@6wind.com>
---
lib/librte_ethdev/rte_ethdev.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index dc6596bc93b4..b423e71050e9 100644
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -4245,8 +4245,8 @@ rte_eth_rx_descriptor_status(uint16_t port_id, uint16_t
queue_id,
* @param queue_id
* A valid Tx queue identifier on this port.
* @param offset
- * The offset of the descriptor starting from tail (0 is the place where
- * the next packet will be send).
+ * The offset of the descriptor starting from tail (0 is the last written
+ * descriptor).
*
* @return
* - (RTE_ETH_TX_DESC_FULL) Descriptor is being processed by the hw, i.e.
The patch lacks explanation why it was wrong before and why it is
correct after the patch.
I think there is a space here for description improvements since it is
still confusing. I'd suggest to remove 'tail' term from the description or
write down full description to explain what/where is head and tail.
Rx case:
V-->offset
=========***********----------------00000000000==
UNAVAIL DONE AVAIL UNUSED
i.e. V points to the next packet to be received by the driver, i.e. the
first *
(the descriptor is done by HW and packet is ready to be processed).
DONE(*) are descriptors filled in by HW, but not processed by the driver
yet.
AVAIL(-) are available for HW to fill in with received packets.
UNUSED(0) (right now it is UNAVAIL as well) are descriptors which can be
done AVAIL on Rx queue refill
UNAVAIL(=) are reserved Rx ring space which cannot be used
The key question for Rx is the length of DONE. Is CPU fast enough to
handle incoming traffic?
Tx case (where is tail V and why):
=========************--------------00000000000==
UNAVAIL DONE FULL UNUSED
DONE(*) are descriptors processed by HW and should be processed by the
driver to
free associated mbuf (rte_eth_tx_done_cleanup())
FULL(-) are available for HW to send these packets out, but not
processed yet.
UNUSED(0) is available space in Tx ring to make it FULL
UNAVAIL(=) is reserved Tx ring space which cannot be used
I'd say that it should be similar to Rx here, but it looks different in
accordance with
current description. Above patch fixes it from the first '-' (or the
first '0'?) to be
the last '-'.
What is the main question for Tx status descriptor user?
