d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

When direct dispatching an netisr (net.isr.enable=1), if there are already

Browse Source 
any queued packets for the isr, process those packets before the newly
submitted packet, maintaining ordering of all packets being delivered
to the netisr.  Remove the bypass counter since we don't bypass anymore.
Leave the comment about possible problems and options since later
performance optimization may change the strategy for addressing ordering
problems here.

Specifically, this maintains the strong isr ordering guarantee; additional
parallelism and lower latency may be possible by moving to weaker
guarantees (per-interface, for example).  We will probably at some point
also want to remove the one instance netisr dispatch limit currently
enforced by a mutex, but it's not clear that's 100% safe yet, even in
the netperf branch.

Reviewed by:	sam, others
This commit is contained in:
rwatson 2003-10-03 18:27:24 +00:00
parent dd70179215
commit a2b04c6504
1 changed files with 21 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
sys/net/netisr.c
View File

@ -100,7 +100,6 @@ struct isrstat {
int isrs_count; /* dispatch count */
int isrs_directed; /* ...successfully dispatched */
int isrs_deferred; /* ...queued instead */
int isrs_bypassed; /* bypassed queued packets */
int isrs_queued; /* intentionally queueued */
int isrs_swi_count; /* swi_net handlers called */
};
@ -119,13 +118,29 @@ SYSCTL_INT(_net_isr, OID_AUTO, directed, CTLFLAG_RD,
&isrstat.isrs_directed, 0, "");
SYSCTL_INT(_net_isr, OID_AUTO, deferred, CTLFLAG_RD,
&isrstat.isrs_deferred, 0, "");
SYSCTL_INT(_net_isr, OID_AUTO, bypassed, CTLFLAG_RD,
&isrstat.isrs_bypassed, 0, "");
SYSCTL_INT(_net_isr, OID_AUTO, queued, CTLFLAG_RD,
&isrstat.isrs_queued, 0, "");
SYSCTL_INT(_net_isr, OID_AUTO, swi_count, CTLFLAG_RD,
&isrstat.isrs_swi_count, 0, "");
/*
* Process all packets currently present in a netisr queue. Used to
* drain an existing set of packets waiting for processing when we
* begin direct dispatch, to avoid processing packets out of order.
*/
static void
netisr_processqueue(struct netisr *ni)
{
struct mbuf *m;
for (;;) {
IF_DEQUEUE(ni->ni_queue, m);
if (m == NULL)
break;
ni->ni_handler(m);
}
}
/*
* Call the netisr directly instead of queueing the packet, if possible.
*
@ -163,10 +178,9 @@ netisr_dispatch(int num, struct mbuf *m)
* b. fallback to queueing the packet,
* c. sweep the issue under the rug and ignore it.
*
* Currently, we do c), and keep a rough event counter.
* Currently, we do a). Previously, we did c).
*/
if (_IF_QLEN(ni->ni_queue) > 0)
isrstat.isrs_bypassed++;
netisr_processqueue(ni);
ni->ni_handler(m);
mtx_unlock(&netisr_mtx);
} else {
@ -204,7 +218,6 @@ static void
swi_net(void *dummy)
{
struct netisr *ni;
struct mbuf *m;
u_int bits;
int i;
#ifdef DEVICE_POLLING
@ -230,12 +243,7 @@ swi_net(void *dummy)
if (ni->ni_queue == NULL)
ni->ni_handler(NULL);
else
for (;;) {
IF_DEQUEUE(ni->ni_queue, m);
if (m == NULL)
break;
ni->ni_handler(m);
}
netisr_processqueue(ni);
}
} while (polling);
mtx_unlock(&netisr_mtx);