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authorDave Barach <dave@barachs.net>2019-05-02 15:48:15 -0400
committerDave Wallace <dwallacelf@gmail.com>2019-05-24 13:56:01 +0000
commit511ce2572a9710835c6722a09a93b4dd80ab7fae (patch)
treee91aa851cab7e9410aaa1a285cee53801bf51310
parent070b810a883d789c97a9d89f56f952e14ed9999a (diff)
Clean up multi-thread barrier-sync hold-down timerstable/1807
Main thread: don't bother with the barrier sync hold-down timer if none of the worker threads are busy. Worker threads: avoid epoll_pwait (10ms timeout) when the control-plane has been active in the last half-second. Cherry-pick a recent dangling reference fix: pool_elt_at_index after e.g. rx callback is required, in case the unix file pool expands. Manual feature backport to 18.07 Change-Id: I745fbb8a12aeda34b0ec7b6dcda66c0e25c3eee1 Signed-off-by: Dave Barach <dave@barachs.net>
-rw-r--r--src/vlib/main.h5
-rw-r--r--src/vlib/threads.c83
-rw-r--r--src/vlib/threads.h17
-rw-r--r--src/vlib/unix/input.c36
4 files changed, 132 insertions, 9 deletions
diff --git a/src/vlib/main.h b/src/vlib/main.h
index 16e4120..894fe9e 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -61,6 +61,9 @@ typedef struct vlib_main_t
CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
/* Instruction level timing state. */
clib_time_t clib_time;
+ /* Offset from main thread time */
+ f64 time_offset;
+ f64 time_last_barrier_release;
/* Time stamp of last node dispatch. */
u64 cpu_time_last_node_dispatch;
@@ -224,7 +227,7 @@ void vlib_worker_loop (vlib_main_t * vm);
always_inline f64
vlib_time_now (vlib_main_t * vm)
{
- return clib_time_now (&vm->clib_time);
+ return clib_time_now (&vm->clib_time) + vm->time_offset;
}
always_inline f64
diff --git a/src/vlib/threads.c b/src/vlib/threads.c
index a946326..1119d82 100644
--- a/src/vlib/threads.c
+++ b/src/vlib/threads.c
@@ -1448,7 +1448,9 @@ vlib_worker_thread_barrier_sync_int (vlib_main_t * vm)
f64 t_entry;
f64 t_open;
f64 t_closed;
+ f64 max_vector_rate;
u32 count;
+ int i;
if (vec_len (vlib_mains) < 2)
return;
@@ -1468,13 +1470,43 @@ vlib_worker_thread_barrier_sync_int (vlib_main_t * vm)
return;
}
+ /*
+ * Need data to decide if we're working hard enough to honor
+ * the barrier hold-down timer.
+ */
+ max_vector_rate = 0.0;
+ for (i = 1; i < vec_len (vlib_mains); i++)
+ max_vector_rate =
+ clib_max (max_vector_rate,
+ vlib_last_vectors_per_main_loop_as_f64 (vlib_mains[i]));
+
vlib_worker_threads[0].barrier_sync_count++;
/* Enforce minimum barrier open time to minimize packet loss */
ASSERT (vm->barrier_no_close_before <= (now + BARRIER_MINIMUM_OPEN_LIMIT));
- while ((now = vlib_time_now (vm)) < vm->barrier_no_close_before)
- ;
+ /*
+ * If any worker thread seems busy, which we define
+ * as a vector rate above 10, we enforce the barrier hold-down timer
+ */
+ if (max_vector_rate > 10.0)
+ {
+ while (1)
+ {
+ now = vlib_time_now (vm);
+ /* Barrier hold-down timer expired? */
+ if (now >= vm->barrier_no_close_before)
+ break;
+ if ((vm->barrier_no_close_before - now)
+ > (2.0 * BARRIER_MINIMUM_OPEN_LIMIT))
+ {
+ clib_warning
+ ("clock change: would have waited for %.4f seconds",
+ (vm->barrier_no_close_before - now));
+ break;
+ }
+ }
+ }
/* Record time of closure */
t_open = now - vm->barrier_epoch;
vm->barrier_epoch = now;
@@ -1559,6 +1591,14 @@ vlib_worker_thread_barrier_release (vlib_main_t * vm)
deadline = now + BARRIER_SYNC_TIMEOUT;
+ /*
+ * Note when we let go of the barrier.
+ * Workers can use this to derive a reasonably accurate
+ * time offset. See vlib_time_now(...)
+ */
+ vm->time_last_barrier_release = vlib_time_now (vm);
+ CLIB_MEMORY_STORE_BARRIER ();
+
*vlib_worker_threads->wait_at_barrier = 0;
while (*vlib_worker_threads->workers_at_barrier > 0)
@@ -1844,6 +1884,45 @@ threads_init (vlib_main_t * vm)
VLIB_INIT_FUNCTION (threads_init);
+
+static clib_error_t *
+show_clock_command_fn (vlib_main_t * vm,
+ unformat_input_t * input, vlib_cli_command_t * cmd)
+{
+ int i;
+ f64 now;
+
+ now = vlib_time_now (vm);
+
+ vlib_cli_output (vm, "Time now %.9f", now);
+
+ if (vec_len (vlib_mains) == 1)
+ return 0;
+
+ vlib_cli_output (vm, "Time last barrier release %.9f",
+ vm->time_last_barrier_release);
+
+ for (i = 1; i < vec_len (vlib_mains); i++)
+ {
+ if (vlib_mains[i] == 0)
+ continue;
+ vlib_cli_output (vm, "Thread %d offset %.9f error %.9f", i,
+ vlib_mains[i]->time_offset,
+ vm->time_last_barrier_release -
+ vlib_mains[i]->time_last_barrier_release);
+ }
+ return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_CLI_COMMAND (f_command, static) =
+{
+ .path = "show clock",
+ .short_help = "show clock",
+ .function = show_clock_command_fn,
+};
+/* *INDENT-ON* */
+
/*
* fd.io coding-style-patch-verification: ON
*
diff --git a/src/vlib/threads.h b/src/vlib/threads.h
index f78ec1b..dd0ed20 100644
--- a/src/vlib/threads.h
+++ b/src/vlib/threads.h
@@ -400,7 +400,7 @@ vlib_worker_thread_barrier_check (void)
{
if (PREDICT_FALSE (*vlib_worker_threads->wait_at_barrier))
{
- vlib_main_t *vm;
+ vlib_main_t *vm = vlib_get_main ();
clib_smp_atomic_add (vlib_worker_threads->workers_at_barrier, 1);
if (CLIB_DEBUG > 0)
{
@@ -409,6 +409,21 @@ vlib_worker_thread_barrier_check (void)
}
while (*vlib_worker_threads->wait_at_barrier)
;
+
+ /*
+ * Recompute the offset from thread-0 time.
+ * Note that vlib_time_now adds vm->time_offset, so
+ * clear it first. Save the resulting idea of "now", to
+ * see how well we're doing. See show_clock_command_fn(...)
+ */
+ {
+ f64 now;
+ vm->time_offset = 0.0;
+ now = vlib_time_now (vm);
+ vm->time_offset = vlib_global_main.time_last_barrier_release - now;
+ vm->time_last_barrier_release = vlib_time_now (vm);
+ }
+
if (CLIB_DEBUG > 0)
vm->parked_at_barrier = 0;
clib_smp_atomic_add (vlib_worker_threads->workers_at_barrier, -1);
diff --git a/src/vlib/unix/input.c b/src/vlib/unix/input.c
index 8be0770..20a98f7 100644
--- a/src/vlib/unix/input.c
+++ b/src/vlib/unix/input.c
@@ -145,9 +145,13 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
vlib_node_main_t *nm = &vm->node_main;
u32 ticks_until_expiration;
f64 timeout;
+ f64 now;
int timeout_ms = 0, max_timeout_ms = 10;
f64 vector_rate = vlib_last_vectors_per_main_loop (vm);
+ if (is_main == 0)
+ now = vlib_time_now (vm);
+
/*
* If we've been asked for a fixed-sleep between main loop polls,
* do so right away.
@@ -194,8 +198,9 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
}
node->input_main_loops_per_call = 0;
}
- else if (is_main == 0 && vector_rate < 2 &&
- nm->input_node_counts_by_state[VLIB_NODE_STATE_POLLING] == 0)
+ else if (is_main == 0 && vector_rate < 2
+ && (vlib_global_main.time_last_barrier_release + 0.5 < now)
+ && nm->input_node_counts_by_state[VLIB_NODE_STATE_POLLING] == 0)
{
timeout = 10e-3;
timeout_ms = max_timeout_ms;
@@ -223,12 +228,32 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
em->epoll_events,
vec_len (em->epoll_events), timeout_ms);
}
+
}
else
{
+ /*
+ * Worker thread, no epoll fd's, sleep for 100us at a time
+ * and check for a barrier sync request
+ */
if (timeout_ms)
- usleep (timeout_ms * 1000);
- return 0;
+ {
+ struct timespec ts, tsrem;
+ f64 limit = now + (f64) timeout_ms * 1e-3;
+
+ while (vlib_time_now (vm) < limit)
+ {
+ /* Sleep for 100us at a time */
+ ts.tv_sec = 0;
+ ts.tv_nsec = 1000 * 100;
+
+ while (nanosleep (&ts, &tsrem) < 0)
+ ts = tsrem;
+ if (*vlib_worker_threads->wait_at_barrier)
+ goto done;
+ }
+ }
+ goto done;
}
}
@@ -238,7 +263,7 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
vlib_panic_with_error (vm, clib_error_return_unix (0, "epoll_wait"));
/* non fatal error (e.g. EINTR). */
- return 0;
+ goto done;
}
em->epoll_waits += 1;
@@ -314,6 +339,7 @@ linux_epoll_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
}
}
+done:
return 0;
}