[lttng-dev] [PATCH lttng-ust] Implement LTTNG_UST_BLOCKING_RETRY_TIMEOUT
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Fri Nov 4 13:44:34 UTC 2016
Add LTTNG_UST_BLOCKING_RETRY_TIMEOUT environment variable:
LTTNG_UST_BLOCKING_RETRY_TIMEOUT
Maximum time during which event tracing retry is attempted on
buffer full condition (millliseconds). Setting this
environment to non-zero value effectively blocks the
application on buffer full condition. Setting this
environment variable to non-zero values may significantly
affect application timings. Setting this to a negative value
may block the application indefinitely if there is no
consumer emptying the ring buffer. This option can be useful
in workloads generating very large trace data throughput,
where blocking the application is an acceptable trade-off to
not discard events. Use with caution.
The value 0 means do not retry. The value -1 means retry
forever.
Default: 0.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
---
configure.ac | 2 ++
doc/man/Makefile.am | 4 +++-
doc/man/lttng-ust.3.txt | 16 ++++++++++++++++
liblttng-ust/lttng-ust-comm.c | 19 ++++++++++++++++++-
libringbuffer/Makefile.am | 2 +-
libringbuffer/{tlsfixup.h => rb-init.h} | 11 ++++++-----
libringbuffer/ring_buffer_frontend.c | 32 +++++++++++++++++++++++++++++++-
7 files changed, 77 insertions(+), 9 deletions(-)
rename libringbuffer/{tlsfixup.h => rb-init.h} (71%)
diff --git a/configure.ac b/configure.ac
index 1add5d6..450b43b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -435,6 +435,8 @@ AC_DEFUN([_AC_DEFINE_AND_SUBST], [
])
_AC_DEFINE_AND_SUBST([LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS], [3000])
+# By default, do not retry on buffer full condition.
+_AC_DEFINE_AND_SUBST([LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS], [0])
AC_CONFIG_FILES([
Makefile
diff --git a/doc/man/Makefile.am b/doc/man/Makefile.am
index 22aed15..449377f 100644
--- a/doc/man/Makefile.am
+++ b/doc/man/Makefile.am
@@ -56,7 +56,9 @@ if HAVE_ASCIIDOC_XMLTO
# Tools to execute:
ADOC = $(ASCIIDOC) -f $(ASCIIDOC_CONF) -d manpage \
-a lttng_version="$(PACKAGE_VERSION)" \
- -a lttng_ust_register_timeout="@LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS@"
+ -a lttng_ust_register_timeout="@LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS@" \
+ -a lttng_ust_blocking_retry_timeout="@LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS@"
+
ADOC_DOCBOOK = $(ADOC) -b docbook
XTO = $(XMLTO) -m $(firstword $(XSL_SRC_FILES)) man
diff --git a/doc/man/lttng-ust.3.txt b/doc/man/lttng-ust.3.txt
index 7a23943..f918998 100644
--- a/doc/man/lttng-ust.3.txt
+++ b/doc/man/lttng-ust.3.txt
@@ -1123,6 +1123,22 @@ with time constraints on the process startup time.
+
Default: {lttng_ust_register_timeout}.
+`LTTNG_UST_BLOCKING_RETRY_TIMEOUT`::
+ Maximum time during which event tracing retry is attempted on buffer
+ full condition (millliseconds). Setting this environment to non-zero
+ value effectively blocks the application on buffer full condition.
+ Setting this environment variable to non-zero values may
+ significantly affect application timings. Setting this to a negative
+ value may block the application indefinitely if there is no consumer
+ emptying the ring buffer. This option can be useful in workloads
+ generating very large trace data throughput, where blocking the
+ application is an acceptable trade-off to not discard events.
+ _Use with caution_.
++
+The value `0` means _do not retry_. The value `-1` means _retry forever_.
++
+Default: {lttng_ust_blocking_retry_timeout}.
+
`LTTNG_UST_WITHOUT_BADDR_STATEDUMP`::
Prevents `liblttng-ust` from performing a base address state dump
(see the <<state-dump,LTTng-UST state dump>> section above) if
diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 7cd6a22..ccdec65 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -52,7 +52,7 @@
#include "tracepoint-internal.h"
#include "lttng-tracer-core.h"
#include "compat.h"
-#include "../libringbuffer/tlsfixup.h"
+#include "../libringbuffer/rb-init.h"
#include "lttng-ust-statedump.h"
#include "clock.h"
#include "../libringbuffer/getcpu.h"
@@ -534,6 +534,21 @@ int get_constructor_timeout(struct timespec *constructor_timeout)
}
static
+void get_blocking_retry_timeout(void)
+{
+ const char *str_blocking_retry_timeout =
+ getenv("LTTNG_UST_BLOCKING_RETRY_TIMEOUT");
+
+ if (str_blocking_retry_timeout) {
+ long timeout = strtol(str_blocking_retry_timeout, NULL, 10);
+
+ if (timeout < 0)
+ timeout = -1;
+ lttng_ust_ringbuffer_set_retry_timeout(timeout);
+ }
+}
+
+static
int register_to_sessiond(int socket, enum ustctl_socket_type type)
{
return ustcomm_send_reg_msg(socket,
@@ -1672,6 +1687,8 @@ void __attribute__((constructor)) lttng_ust_init(void)
timeout_mode = get_constructor_timeout(&constructor_timeout);
+ get_blocking_retry_timeout();
+
ret = sem_init(&constructor_wait, 0, 0);
if (ret) {
PERROR("sem_init");
diff --git a/libringbuffer/Makefile.am b/libringbuffer/Makefile.am
index 271c8be..33db165 100644
--- a/libringbuffer/Makefile.am
+++ b/libringbuffer/Makefile.am
@@ -11,7 +11,7 @@ libringbuffer_la_SOURCES = \
api.h \
backend.h backend_internal.h backend_types.h \
frontend_api.h frontend.h frontend_internal.h frontend_types.h \
- nohz.h vatomic.h tlsfixup.h
+ nohz.h vatomic.h rb-init.h
libringbuffer_la_LIBADD = \
-lpthread \
diff --git a/libringbuffer/tlsfixup.h b/libringbuffer/rb-init.h
similarity index 71%
rename from libringbuffer/tlsfixup.h
rename to libringbuffer/rb-init.h
index 125742e..eba087f 100644
--- a/libringbuffer/tlsfixup.h
+++ b/libringbuffer/rb-init.h
@@ -1,10 +1,10 @@
-#ifndef _LTTNG_UST_LIB_RINGBUFFER_TLS_FIXUP_H
-#define _LTTNG_UST_LIB_RINGBUFFER_TLS_FIXUP_H
+#ifndef _LTTNG_UST_LIB_RINGBUFFER_RB_INIT_H
+#define _LTTNG_UST_LIB_RINGBUFFER_RB_INIT_H
/*
- * libringbuffer/tlsfixup.h
+ * libringbuffer/rb-init.h
*
- * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
+ * Copyright (C) 2012-2016 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
@@ -22,5 +22,6 @@
*/
void lttng_fixup_ringbuffer_tls(void);
+void lttng_ust_ringbuffer_set_retry_timeout(int timeout);
-#endif /* _LTTNG_UST_LIB_RINGBUFFER_TLS_FIXUP_H */
+#endif /* _LTTNG_UST_LIB_RINGBUFFER_RB_INIT_H */
diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index be20d69..c062e0c 100644
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -72,7 +72,7 @@
#include "backend.h"
#include "frontend.h"
#include "shm.h"
-#include "tlsfixup.h"
+#include "rb-init.h"
#include "../liblttng-ust/compat.h" /* For ENODATA */
/* Print DBG() messages about events lost only every 1048576 hits */
@@ -84,6 +84,7 @@
#define CLOCKID CLOCK_MONOTONIC
#define LTTNG_UST_RING_BUFFER_GET_RETRY 10
#define LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS 10
+#define RETRY_DELAY 100 /* 100 ms. */
/*
* Non-static to ensure the compiler does not optimize away the xor.
@@ -149,6 +150,14 @@ static struct timer_signal_data timer_signal = {
.lock = PTHREAD_MUTEX_INITIALIZER,
};
+int lttng_ust_blocking_retry_timeout =
+ CONFIG_LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS;
+
+void lttng_ust_ringbuffer_set_retry_timeout(int timeout)
+{
+ lttng_ust_blocking_retry_timeout = timeout;
+}
+
/**
* lib_ring_buffer_reset - Reset ring buffer to initial values.
* @buf: Ring buffer.
@@ -1985,6 +1994,23 @@ void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, enum swi
lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc, handle);
}
+static
+bool handle_blocking_retry(int *timeout_left_ms)
+{
+ int timeout = *timeout_left_ms, delay;
+
+ if (caa_likely(!timeout))
+ return false; /* Do not retry, discard event. */
+ if (timeout < 0) /* Wait forever. */
+ delay = RETRY_DELAY;
+ else
+ delay = min_t(int, timeout, RETRY_DELAY);
+ (void) poll(NULL, 0, delay);
+ if (timeout > 0)
+ *timeout_left_ms -= delay;
+ return true; /* Retry. */
+}
+
/*
* Returns :
* 0 if ok
@@ -2001,6 +2027,7 @@ int lib_ring_buffer_try_reserve_slow(struct lttng_ust_lib_ring_buffer *buf,
const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
struct lttng_ust_shm_handle *handle = ctx->handle;
unsigned long reserve_commit_diff, offset_cmp;
+ int timeout_left_ms = lttng_ust_blocking_retry_timeout;
retry:
offsets->begin = offset_cmp = v_read(config, &buf->offset);
@@ -2083,6 +2110,9 @@ retry:
>= chan->backend.buf_size)) {
unsigned long nr_lost;
+ if (handle_blocking_retry(&timeout_left_ms))
+ goto retry;
+
/*
* We do not overwrite non consumed buffers
* and we are full : record is lost.
--
2.1.4
More information about the lttng-dev
mailing list