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net/tcp/tcp_recvwindow.c: In order to receive data we must not only have IOBs available, but we must also have at least one IOB chain qentry available. Otherwise, we will advertise that we an buffer a lot of data when, in fact, we cannot. This is an expermental fix to a performance problem noted by Masayuki Ishikawa.

This commit is contained in:
Gregory Nutt 2018-09-22 09:33:05 -06:00
parent 510b0f7e07
commit dec7ecbd56
3 changed files with 22 additions and 17 deletions
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4
include/nuttx/mm/iob.h
View File

@ -198,14 +198,14 @@ FAR struct iob_s *iob_tryalloc(bool throttled);
int iob_navail(bool throttled);
/****************************************************************************
* Name: iob_quentry_navail
* Name: iob_qentry_navail
*
* Description:
* Return the number of available IOB chains.
*
****************************************************************************/
int iob_quentry_navail(void);
int iob_qentry_navail(void);
/****************************************************************************
* Name: iob_free

4
mm/iob/iob_navail.c
View File

@ -93,14 +93,14 @@ int iob_navail(bool throttled)
}
/****************************************************************************
* Name: iob_quentry_navail
* Name: iob_qentry_navail
*
* Description:
* Return the number of available IOB chains.
*
****************************************************************************/
int iob_quentry_navail(void)
int iob_qentry_navail(void)
{
int navail = 0;
int ret;

31
net/tcp/tcp_recvwindow.c
View File

@ -76,7 +76,8 @@ uint16_t tcp_get_recvwindow(FAR struct net_driver_s *dev)
uint16_t mss;
uint16_t recvwndo;
#ifdef CONFIG_NET_TCP_READAHEAD
int navail;
int niob_avail;
int nqentry_avail;
#endif
#ifdef CONFIG_NET_IPv6
@ -107,10 +108,14 @@ uint16_t tcp_get_recvwindow(FAR struct net_driver_s *dev)
#ifdef CONFIG_NET_TCP_READAHEAD
/* Update the TCP received window based on read-ahead I/O buffer
* availability.
* and IOB chain availability. At least one queue entry is required.
* If one queue entry is available, then the amount of read-ahead
* data that can be buffered is given by the number of IOBs available
* (ignoring competition with other IOB consumers).
*/
navail = iob_navail(true);
niob_avail = iob_navail(true);
nqentry_avail = iob_qentry_navail();
/* Are the read-ahead allocations throttled? If so, then not all of these
* IOBs are available for read-ahead buffering.
@ -120,19 +125,19 @@ uint16_t tcp_get_recvwindow(FAR struct net_driver_s *dev)
*/
#if CONFIG_IOB_THROTTLE > 0
if (navail > CONFIG_IOB_THROTTLE)
if (niob_avail > CONFIG_IOB_THROTTLE)
{
navail -= CONFIG_IOB_THROTTLE;
niob_avail -= CONFIG_IOB_THROTTLE;
}
else
{
navail = 0;
niob_avail = 0;
}
#endif
/* Are there any IOBs available for read-ahead buffering? */
/* Is there a a queue entry and IOBs available for read-ahead buffering? */
if (navail > 0)
if (nqentry_avail > 0 && niob_avail > 0)
{
uint32_t rwnd;
@ -152,7 +157,7 @@ uint16_t tcp_get_recvwindow(FAR struct net_driver_s *dev)
* buffering for this connection.
*/
rwnd = (navail * CONFIG_IOB_BUFSIZE) + mss;
rwnd = (niob_avail * CONFIG_IOB_BUFSIZE) + mss;
if (rwnd > UINT16_MAX)
{
rwnd = UINT16_MAX;
@ -162,12 +167,12 @@ uint16_t tcp_get_recvwindow(FAR struct net_driver_s *dev)
recvwndo = (uint16_t)rwnd;
}
else /* if (navail == 0) */
else /* nqentry_avail == 0 || niob_avail == 0 */
#endif
{
/* No IOBs are available. The only buffering available is within the
* packet buffer itself. We can buffer no more than the MSS (unless
* we are very fast).
/* No IOB chains or noIOBs are available. The only buffering
* available is within the packet buffer itself. We can buffer no
* more than the MSS (unless we are very fast).
*
* NOTE: If no IOBs are available, then the next packet will be
* lost if there is no listener on the connection.