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diff --git a/sys/kern/subr_trap.c b/sys/kern/subr_trap.c
--- a/sys/kern/subr_trap.c
+++ b/sys/kern/subr_trap.c
@@ -74,6 +74,8 @@
#include <sys/epoch.h>
#endif
+void (*tcp_hpts_softclock)(void);
+
/*
* Define the code needed before returning to user mode, for trap and
* syscall.
@@ -125,16 +127,18 @@
if (PMC_THREAD_HAS_SAMPLES(td))
PMC_CALL_HOOK(td, PMC_FN_THR_USERRET, NULL);
#endif
-#ifdef TCPHPTS
/*
- * @gallatin is adament that this needs to go here, I
- * am not so sure. Running hpts is a lot like
- * a lro_flush() that happens while a user process
- * is running. But he may know best so I will go
- * with his view of accounting. :-)
+ * Calling tcp_hpts_softclock() here allows us to avoid frequent,
+ * expensive callouts that trash the cache and lead to a much higher
+ * number of interrupts and context switches. Testing on busy web
+ * servers at Netflix has shown that this improves CPU use by 7% over
+ * relying only on callouts to drive HPTS, and also results in idle
+ * power savings on mostly idle servers.
+ * This was inspired by the paper "Soft Timers: Efficient Microsecond
+ * Software Timer Support for Network Processing"
+ * by Mohit Aron and Peter Druschel.
*/
- tcp_run_hpts();
-#endif
+ tcp_hpts_softclock();
/*
* Let the scheduler adjust our priority etc.
*/
diff --git a/sys/netinet/tcp_hpts.h b/sys/netinet/tcp_hpts.h
--- a/sys/netinet/tcp_hpts.h
+++ b/sys/netinet/tcp_hpts.h
@@ -152,7 +152,6 @@
void tcp_set_inp_to_drop(struct inpcb *inp, uint16_t reason);
-extern void (*tcp_hpts_softclock)(void);
void tcp_lro_hpts_init(void);
extern int32_t tcp_min_hptsi_time;
diff --git a/sys/netinet/tcp_lro.c b/sys/netinet/tcp_lro.c
--- a/sys/netinet/tcp_lro.c
+++ b/sys/netinet/tcp_lro.c
@@ -89,7 +89,6 @@
long tcplro_stacks_wanting_mbufq;
int (*tcp_lro_flush_tcphpts)(struct lro_ctrl *lc, struct lro_entry *le);
-void (*tcp_hpts_softclock)(void);
counter_u64_t tcp_inp_lro_direct_queue;
counter_u64_t tcp_inp_lro_wokeup_queue;
@@ -1262,8 +1261,7 @@
done:
/* flush active streams */
tcp_lro_rx_done(lc);
- if (tcp_hpts_softclock != NULL)
- tcp_hpts_softclock();
+ tcp_hpts_softclock();
lc->lro_mbuf_count = 0;
}
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -378,6 +378,12 @@
extern int cpu_disable_c2_sleep;
extern int cpu_disable_c3_sleep;
+extern void (*tcp_hpts_softclock)(void);
+#define tcp_hpts_softclock() do { \
+ if (tcp_hpts_softclock != NULL) \
+ tcp_hpts_softclock(); \
+} while (0)
+
char *kern_getenv(const char *name);
void freeenv(char *env);
int getenv_int(const char *name, int *data);

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