linux-kernel - [PATCH v3 net-next 1/4] net: convert low latency sockets to sched

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Message-ID: <20130613144623.4875.2539.stgit@ladj378.jer.intel.com>
Date:	Thu, 13 Jun 2013 17:46:23 +0300
From:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
To:	David Miller <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	e1000-devel@...ts.sourceforge.net,
	Willem de Bruijn <willemb@...gle.com>,
	Eric Dumazet <erdnetdev@...il.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Amir Vadai <amirv@...lanox.com>,
	Alex Rosenbaum <alexr@...lanox.com>,
	Avner Ben Hanoch <avnerb@...lanox.com>,
	Or Kehati <ork@...lanox.com>, sockperf-dev@...glegroups.com,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: [PATCH v3 net-next 1/4] net: convert low latency sockets to
 sched_clock()

Use sched_clock() instead of get_cycles().
We can use sched_clock() because we don't care much about accuracy.
Remove the dependency on X86_TSC

Signed-off-by: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
---

 include/net/ll_poll.h |   23 +++++++++++------------
 net/Kconfig           |    1 -
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/include/net/ll_poll.h b/include/net/ll_poll.h
index bc262f8..c75a611 100644
--- a/include/net/ll_poll.h
+++ b/include/net/ll_poll.h
@@ -21,10 +21,6 @@
  * e1000-devel Mailing List <e1000-devel@...ts.sourceforge.net>
  */
 
-/*
- * For now this depends on CONFIG_X86_TSC
- */
-
 #ifndef _LINUX_NET_LL_POLL_H
 #define _LINUX_NET_LL_POLL_H
 
@@ -41,11 +37,14 @@ extern unsigned long sysctl_net_ll_poll __read_mostly;
 #define LL_FLUSH_BUSY		-2
 
 /* we don't mind a ~2.5% imprecision */
-#define TSC_MHZ (tsc_khz >> 10)
+#define USECS_TO_NS(us) (us << 10)
 
-static inline cycles_t ll_end_time(void)
+/* we can use sched_clock() because we don't care much about precision
+ * we only care that the average is bounded
+ */
+static inline u64 ll_end_time(void)
 {
-	return TSC_MHZ * ACCESS_ONCE(sysctl_net_ll_poll) + get_cycles();
+	return sched_clock() + USECS_TO_NS(ACCESS_ONCE(sysctl_net_ll_poll));
 }
 
 static inline bool sk_valid_ll(struct sock *sk)
@@ -54,16 +53,16 @@ static inline bool sk_valid_ll(struct sock *sk)
 	       !need_resched() && !signal_pending(current);
 }
 
-static inline bool can_poll_ll(cycles_t end_time)
+static inline bool can_poll_ll(u64 end_time)
 {
-	return !time_after((unsigned long)get_cycles(),
+	return !time_after((unsigned long)sched_clock(),
 			    (unsigned long)end_time);
 }
 
 static inline bool sk_poll_ll(struct sock *sk, int nonblock)
 {
-	cycles_t end_time = ll_end_time();
 	const struct net_device_ops *ops;
+	u64 end_time = ll_end_time();
 	struct napi_struct *napi;
 	int rc = false;
 
@@ -116,7 +115,7 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
 
 #else /* CONFIG_NET_LL_RX_POLL */
 
-static inline cycles_t ll_end_time(void)
+static inline u64 ll_end_time(void)
 {
 	return 0;
 }
@@ -139,7 +138,7 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
 {
 }
 
-static inline bool can_poll_ll(cycles_t end_time)
+static inline bool can_poll_ll(u64 end_time)
 {
 	return false;
 }
diff --git a/net/Kconfig b/net/Kconfig
index d6a9ce6..e591668 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -245,7 +245,6 @@ config NETPRIO_CGROUP
 
 config NET_LL_RX_POLL
 	bool "Low Latency Receive Poll"
-	depends on X86_TSC
 	default n
 	---help---
 	  Support Low Latency Receive Queue Poll.

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