add network latency patches

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

3 files changed, 155 insertions, 0 deletions

diff --git a/queue/net-reduce-net_rx_action-latency-to-2-HZ.patch b/queue/net-reduce-net_rx_action-latency-to-2-HZ.patch
new file mode 100644
index 0000000..f10ebc2
--- /dev/null
+++ b/queue/net-reduce-net_rx_action-latency-to-2-HZ.patch
@@ -0,0 +1,32 @@
+From 1e6fac40ce92bddccdd0ac30a92a0a11b20c73f8 Mon Sep 17 00:00:00 2001
+From: Eric Dumazet <edumazt@google.com>
+Date: Tue, 5 Mar 2013 07:15:13 +0000
+Subject: [PATCH] net: reduce net_rx_action() latency to 2 HZ
+
+commit d1f41b67ff7735193bc8b418b98ac99a448833e2 upstream.
+
+We should use time_after_eq() to get maximum latency of two ticks,
+instead of three.
+
+Bug added in commit 24f8b2385 (net: increase receive packet quantum)
+
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
+
+diff --git a/net/core/dev.c b/net/core/dev.c
+index 2aaf2e6..253b409 100644
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -3045,7 +3045,7 @@ static void net_rx_action(struct softirq_action *h)
+ 		 * Allow this to run for 2 jiffies since which will allow
+ 		 * an average latency of 1.5/HZ.
+ 		 */
+-		if (unlikely(budget <= 0 || time_after(jiffies, time_limit)))
++		if (unlikely(budget <= 0 || time_after_eq(jiffies, time_limit)))
+ 			goto softnet_break;
+ 
+ 		local_irq_enable();
+-- 
+1.8.1.2
+
diff --git a/queue/series b/queue/series
index 981e29b..f04bcfd 100644
--- a/queue/series
+++ b/queue/series
@@ -5,3 +5,5 @@ hugetlb-fix-resv_map-leak-in-error-path.patch
 mm-fix-vma_resv_map-NULL-pointer.patch
 ext4-Fix-fs-corruption-when-make_indexed_dir-fails.patch
 ext4-don-t-dereference-null-pointer-when-make_indexe.patch
+net-reduce-net_rx_action-latency-to-2-HZ.patch
+softirq-reduce-latencies.patch
diff --git a/queue/softirq-reduce-latencies.patch b/queue/softirq-reduce-latencies.patch
new file mode 100644
index 0000000..d995dc4
--- /dev/null
+++ b/queue/softirq-reduce-latencies.patch
@@ -0,0 +1,121 @@
+From 8476a73f215d49e021a0d04f879231fff8ae6e9b Mon Sep 17 00:00:00 2001
+From: Eric Dumazet <edumazet@google.com>
+Date: Thu, 10 Jan 2013 15:26:34 -0800
+Subject: [PATCH] softirq: reduce latencies
+
+commit c10d73671ad30f54692f7f69f0e09e75d3a8926a upstream.
+
+In various network workloads, __do_softirq() latencies can be up
+to 20 ms if HZ=1000, and 200 ms if HZ=100.
+
+This is because we iterate 10 times in the softirq dispatcher,
+and some actions can consume a lot of cycles.
+
+This patch changes the fallback to ksoftirqd condition to :
+
+- A time limit of 2 ms.
+- need_resched() being set on current task
+
+When one of this condition is met, we wakeup ksoftirqd for further
+softirq processing if we still have pending softirqs.
+
+Using need_resched() as the only condition can trigger RCU stalls,
+as we can keep BH disabled for too long.
+
+I ran several benchmarks and got no significant difference in
+throughput, but a very significant reduction of latencies (one order
+of magnitude) :
+
+In following bench, 200 antagonist "netperf -t TCP_RR" are started in
+background, using all available cpus.
+
+Then we start one "netperf -t TCP_RR", bound to the cpu handling the NIC
+IRQ (hard+soft)
+
+Before patch :
+
+# netperf -H 7.7.7.84 -t TCP_RR -T2,2 -- -k
+RT_LATENCY,MIN_LATENCY,MAX_LATENCY,P50_LATENCY,P90_LATENCY,P99_LATENCY,MEAN_LATENCY,STDDEV_LATENCY
+MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
+to 7.7.7.84 () port 0 AF_INET : first burst 0 : cpu bind
+RT_LATENCY=550110.424
+MIN_LATENCY=146858
+MAX_LATENCY=997109
+P50_LATENCY=305000
+P90_LATENCY=550000
+P99_LATENCY=710000
+MEAN_LATENCY=376989.12
+STDDEV_LATENCY=184046.92
+
+After patch :
+
+# netperf -H 7.7.7.84 -t TCP_RR -T2,2 -- -k
+RT_LATENCY,MIN_LATENCY,MAX_LATENCY,P50_LATENCY,P90_LATENCY,P99_LATENCY,MEAN_LATENCY,STDDEV_LATENCY
+MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
+to 7.7.7.84 () port 0 AF_INET : first burst 0 : cpu bind
+RT_LATENCY=40545.492
+MIN_LATENCY=9834
+MAX_LATENCY=78366
+P50_LATENCY=33583
+P90_LATENCY=59000
+P99_LATENCY=69000
+MEAN_LATENCY=38364.67
+STDDEV_LATENCY=12865.26
+
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Cc: David Miller <davem@davemloft.net>
+Cc: Tom Herbert <therbert@google.com>
+Cc: Ben Hutchings <bhutchings@solarflare.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
+
+diff --git a/kernel/softirq.c b/kernel/softirq.c
+index 7c1a67e..0df9a94 100644
+--- a/kernel/softirq.c
++++ b/kernel/softirq.c
+@@ -178,21 +178,21 @@ void local_bh_enable_ip(unsigned long ip)
+ EXPORT_SYMBOL(local_bh_enable_ip);
+ 
+ /*
+- * We restart softirq processing MAX_SOFTIRQ_RESTART times,
+- * and we fall back to softirqd after that.
++ * We restart softirq processing for at most 2 ms,
++ * and if need_resched() is not set.
+  *
+- * This number has been established via experimentation.
++ * These limits have been established via experimentation.
+  * The two things to balance is latency against fairness -
+  * we want to handle softirqs as soon as possible, but they
+  * should not be able to lock up the box.
+  */
+-#define MAX_SOFTIRQ_RESTART 10
++#define MAX_SOFTIRQ_TIME  msecs_to_jiffies(2)
+ 
+ asmlinkage void __do_softirq(void)
+ {
+ 	struct softirq_action *h;
+ 	__u32 pending;
+-	int max_restart = MAX_SOFTIRQ_RESTART;
++	unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
+ 	int cpu;
+ 
+ 	pending = local_softirq_pending();
+@@ -236,11 +236,12 @@ restart:
+ 	local_irq_disable();
+ 
+ 	pending = local_softirq_pending();
+-	if (pending && --max_restart)
+-		goto restart;
++	if (pending) {
++		if (time_before(jiffies, end) && !need_resched())
++			goto restart;
+ 
+-	if (pending)
+ 		wakeup_softirqd();
++	}
+ 
+ 	lockdep_softirq_exit();
+ 
+-- 
+1.8.1.2
+