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From: Juli Mallett <jmallett@FreeBSD.org>
Date: Sun, 9 Jan 2011 23:46:24 +0000 (UTC)
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Subject: svn commit: r217212 - head/sys/mips/cavium/octe
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Author: jmallett
Date: Sun Jan  9 23:46:24 2011
New Revision: 217212
URL: http://svn.freebsd.org/changeset/base/217212

Log:
  Now that we correctly enable rx interrupts on all cores, performance has gotten
  quite awful, because e.g. 4 packets will come in and get processed on 4
  different cores at the same time, really battling with the TCP stack quite
  painfully.  For now, just run one task at a time.
  
  This gets performance up in most cases to where it was before the correctness
  fixes that got interrupts to run on all cores (except in high-load TCP transmit
  cases where all we're handling receive for is ACKs) and in some cases it's
  better now.  What would be ideal would be to use a more advanced interrupt
  mitigation strategy and possibly to use different workqueue groups per port for
  multi-port systems, and so on, but this is a fine stopgap.

Modified:
  head/sys/mips/cavium/octe/ethernet-rx.c

Modified: head/sys/mips/cavium/octe/ethernet-rx.c
==============================================================================
--- head/sys/mips/cavium/octe/ethernet-rx.c	Sun Jan  9 23:20:01 2011	(r217211)
+++ head/sys/mips/cavium/octe/ethernet-rx.c	Sun Jan  9 23:46:24 2011	(r217212)
@@ -54,6 +54,8 @@ extern struct ifnet *cvm_oct_device[];
 static struct task cvm_oct_task;
 static struct taskqueue *cvm_oct_taskq;
 
+static int cvm_oct_rx_active;
+
 /**
  * Interrupt handler. The interrupt occurs whenever the POW
  * transitions from 0->1 packets in our group.
@@ -70,7 +72,13 @@ int cvm_oct_do_interrupt(void *dev_id)
 		cvmx_write_csr(CVMX_POW_WQ_INT, 1<<pow_receive_group);
 	else
 		cvmx_write_csr(CVMX_POW_WQ_INT, 0x10001<<pow_receive_group);
-	taskqueue_enqueue(cvm_oct_taskq, &cvm_oct_task);
+
+	/*
+	 * Schedule task if there isn't one running.
+	 */
+	if (atomic_cmpset_int(&cvm_oct_rx_active, 0, 1))
+		taskqueue_enqueue(cvm_oct_taskq, &cvm_oct_task);
+
 	return FILTER_HANDLED;
 }
 
@@ -353,6 +361,19 @@ void cvm_oct_tasklet_rx(void *context, i
 			cvm_oct_free_work(work);
 	}
 
+	/*
+	 * If we hit our limit, schedule another task while we clean up.
+	 */
+	if (INTERRUPT_LIMIT != 0 && rx_count == MAX_RX_PACKETS) {
+		taskqueue_enqueue(cvm_oct_taskq, &cvm_oct_task);
+	} else {
+		/*
+		 * No more packets, all done.
+		 */
+		if (!atomic_cmpset_int(&cvm_oct_rx_active, 1, 0))
+			panic("%s: inconsistent rx active state.", __func__);
+	}
+
 	/* Restore the original POW group mask */
 	cvmx_write_csr(CVMX_POW_PP_GRP_MSKX(coreid), old_group_mask);
 	if (USE_ASYNC_IOBDMA) {