Introduce the LTTNG_UST_ALLOW_BLOCKING env. var. to control whether
applications are allowed to block when a buffer is full. If set, it
allows the tracer to block the application when buffers are full.
The blocking is now controlled by a per-channel configuration option in
the LTTng control interface for channels with the "--blocking-timeout"
parameter, which is specified in usec (or -1 to block forever).
This replaces the LTTNG_UST_BLOCKING_RETRY_TIMEOUT env. var., which
actually never made it into a stable release (we therefore remove this
env. var).
Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
---
configure.ac | 4 +--
doc/man/Makefile.am | 3 +--
doc/man/lttng-ust.3.txt | 28 ++++++--------------
include/lttng/ust-abi.h | 7 ++++-
include/lttng/ust-ctl.h | 1 +
include/lttng/ust-events.h | 3 ++-
liblttng-ust-ctl/ustctl.c | 3 ++-
liblttng-ust/getenv.c | 2 +-
liblttng-ust/lttng-ring-buffer-client.h | 5 ++--
liblttng-ust/lttng-ring-buffer-metadata-client.h | 5 ++--
liblttng-ust/lttng-ust-comm.c | 29 +++++++--------------
libringbuffer/frontend.h | 3 ++-
libringbuffer/frontend_types.h | 8 +++++-
libringbuffer/rb-init.h | 2 +-
libringbuffer/ring_buffer_frontend.c | 33 +++++++++++++++++++-----
15 files changed, 74 insertions(+), 62 deletions(-)
diff --git a/configure.ac b/configure.ac
index 2440cab..e2acfa9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -26,7 +26,7 @@ AC_SUBST([LTTNG_UST_LIBRARY_VERSION], [0:0:0])
# This is the library version of liblttng-ust-ctl, used internally by
# liblttng-ust, lttng-sessiond, and lttng-consumerd.
-AC_SUBST([LTTNG_UST_CTL_LIBRARY_VERSION], [3:0:1])
+AC_SUBST([LTTNG_UST_CTL_LIBRARY_VERSION], [4:0:0])
AC_CONFIG_HEADERS([config.h include/lttng/ust-config.h])
AC_CONFIG_AUX_DIR([config])
@@ -463,8 +463,6 @@ 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])
AM_CFLAGS="-Wall"
AC_SUBST(AM_CFLAGS)
diff --git a/doc/man/Makefile.am b/doc/man/Makefile.am
index 449377f..3d8ee49 100644
--- a/doc/man/Makefile.am
+++ b/doc/man/Makefile.am
@@ -56,8 +56,7 @@ 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_blocking_retry_timeout="@LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS@"
+ -a
lttng_ust_register_timeout="@LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS@"
ADOC_DOCBOOK = $(ADOC) -b docbook
XTO = $(XMLTO) -m $(firstword $(XSL_SRC_FILES)) man
diff --git a/doc/man/lttng-ust.3.txt b/doc/man/lttng-ust.3.txt
index 21f6098..28d66f2 100644
--- a/doc/man/lttng-ust.3.txt
+++ b/doc/man/lttng-ust.3.txt
@@ -1292,31 +1292,19 @@ LTTng session and consumer daemons (part of the
LTTng-tools project)
are located in a specific directory under `$LTTNG_HOME` (or `$HOME` if
`$LTTNG_HOME` is not set).
-`LTTNG_UST_BLOCKING_RETRY_TIMEOUT`::
- Maximum duration (milliseconds) to retry event tracing when
- there's no space left for the event record in the sub-buffer.
-+
---
-`0`::
- Never block the application.
-
-Positive value::
- Block the application for the specified number of milliseconds. If
- there's no space left after this duration, discard the event
- record.
-
-Negative value::
- Block the application until there's space left for the event record.
---
-+
-Default: {lttng_ust_blocking_retry_timeout}.
+`LTTNG_UST_ALLOW_BLOCKING`::
+ If set, allow application to retry event tracing when there's
+ no space left for the event record in the sub-buffer, therefore
+ effectively blocking the application until space is made available
+ or timeout is reached. This only has effect on channels with
+ `blocking-timeout` set.
+
This option can be useful in workloads generating very large trace data
throughput, where blocking the application is an acceptable trade-off to
prevent discarding event records.
+
-WARNING: Setting this environment variable to a non-zero value may
-significantly affect application timings.
+WARNING: Setting this environment variable may significantly
+affect application timings.
`LTTNG_UST_CLOCK_PLUGIN`::
Path to the shared object which acts as the clock override plugin.
diff --git a/include/lttng/ust-abi.h b/include/lttng/ust-abi.h
index f76d2a9..4976b1b 100644
--- a/include/lttng/ust-abi.h
+++ b/include/lttng/ust-abi.h
@@ -177,7 +177,12 @@ struct lttng_ust_channel_attr {
unsigned int switch_timer_interval; /* usec */
unsigned int read_timer_interval; /* usec */
enum lttng_ust_output output; /* splice, mmap */
- char padding[LTTNG_UST_CHANNEL_ATTR_PADDING];
+ union {
+ struct {
+ int64_t blocking_timeout; /* Blocking timeout
(usec) */
+ } s;
+ char padding[LTTNG_UST_CHANNEL_ATTR_PADDING];
+ } u;
} LTTNG_PACKED;
#define LTTNG_UST_TRACEPOINT_ITER_PADDING 16
diff --git a/include/lttng/ust-ctl.h b/include/lttng/ust-ctl.h
index f6c1dc4..f83124d 100644
--- a/include/lttng/ust-ctl.h
+++ b/include/lttng/ust-ctl.h
@@ -53,6 +53,7 @@ struct ustctl_consumer_channel_attr {
enum lttng_ust_output output; /* splice, mmap */
uint32_t chan_id; /* channel ID */
unsigned char uuid[LTTNG_UST_UUID_LEN]; /* Trace session unique ID */
+ int64_t blocking_timeout; /* Blocking timeout
(usec) */
} LTTNG_PACKED;
/*
diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 6b7bd00..caf7e63 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -489,7 +489,8 @@ struct lttng_channel_ops {
unsigned int read_timer_interval,
unsigned char *uuid,
uint32_t chan_id,
- const int *stream_fds, int nr_stream_fds);
+ const int *stream_fds, int nr_stream_fds,
+ int64_t blocking_timeout);
void (*channel_destroy)(struct lttng_channel *chan);
union {
void *_deprecated1;
diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index 8e2e8f1..8c38ffa 100644
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -1057,7 +1057,8 @@ struct ustctl_consumer_channel *
attr->switch_timer_interval,
attr->read_timer_interval,
attr->uuid, attr->chan_id,
- stream_fds, nr_stream_fds);
+ stream_fds, nr_stream_fds,
+ attr->blocking_timeout);
if (!chan->chan) {
goto chan_error;
}
diff --git a/liblttng-ust/getenv.c b/liblttng-ust/getenv.c
index b4dc73a..25740a5 100644
--- a/liblttng-ust/getenv.c
+++ b/liblttng-ust/getenv.c
@@ -50,7 +50,7 @@ static struct lttng_env lttng_env[] = {
/* Env. var. which are not fetched in setuid/setgid executables. */
{ "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, },
{ "LTTNG_UST_GETCPU_PLUGIN", LTTNG_ENV_SECURE, NULL, },
- { "LTTNG_UST_BLOCKING_RETRY_TIMEOUT", LTTNG_ENV_SECURE, NULL, },
+ { "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, },
{ "HOME", LTTNG_ENV_SECURE, NULL, },
{ "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, },
};
diff --git a/liblttng-ust/lttng-ring-buffer-client.h
b/liblttng-ust/lttng-ring-buffer-client.h
index 6ed0671..52c759f 100644
--- a/liblttng-ust/lttng-ring-buffer-client.h
+++ b/liblttng-ust/lttng-ring-buffer-client.h
@@ -658,7 +658,8 @@ struct lttng_channel *_channel_create(const char *name,
unsigned int read_timer_interval,
unsigned char *uuid,
uint32_t chan_id,
- const int *stream_fds, int nr_stream_fds)
+ const int *stream_fds, int nr_stream_fds,
+ int64_t blocking_timeout)
{
struct lttng_channel chan_priv_init;
struct lttng_ust_shm_handle *handle;
@@ -674,7 +675,7 @@ struct lttng_channel *_channel_create(const char *name,
&chan_priv_init,
buf_addr, subbuf_size, num_subbuf,
switch_timer_interval, read_timer_interval,
- stream_fds, nr_stream_fds);
+ stream_fds, nr_stream_fds, blocking_timeout);
if (!handle)
return NULL;
lttng_chan = priv;
diff --git a/liblttng-ust/lttng-ring-buffer-metadata-client.h
b/liblttng-ust/lttng-ring-buffer-metadata-client.h
index af5162f..00876b5 100644
--- a/liblttng-ust/lttng-ring-buffer-metadata-client.h
+++ b/liblttng-ust/lttng-ring-buffer-metadata-client.h
@@ -206,7 +206,8 @@ struct lttng_channel *_channel_create(const char *name,
unsigned int read_timer_interval,
unsigned char *uuid,
uint32_t chan_id,
- const int *stream_fds, int nr_stream_fds)
+ const int *stream_fds, int nr_stream_fds,
+ int64_t blocking_timeout)
{
struct lttng_channel chan_priv_init;
struct lttng_ust_shm_handle *handle;
@@ -222,7 +223,7 @@ struct lttng_channel *_channel_create(const char *name,
&chan_priv_init,
buf_addr, subbuf_size, num_subbuf,
switch_timer_interval, read_timer_interval,
- stream_fds, nr_stream_fds);
+ stream_fds, nr_stream_fds, blocking_timeout);
if (!handle)
return NULL;
lttng_chan = priv;
diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 43728ff..511b9cf 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -535,26 +535,15 @@ int get_constructor_timeout(struct timespec
*constructor_timeout)
}
static
-void get_blocking_retry_timeout(void)
+void get_allow_blocking(void)
{
- const char *str_blocking_retry_timeout =
- lttng_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;
- if (timeout > INT_MAX) {
- WARN("Saturating %s value from %ld to %d\n",
- "LTTNG_UST_BLOCKING_RETRY_TIMEOUT",
- timeout, INT_MAX);
- timeout = INT_MAX;
- }
- DBG("%s environment variable value is %ld",
- "LTTNG_UST_BLOCKING_RETRY_TIMEOUT",
- timeout);
- lttng_ust_ringbuffer_set_retry_timeout(timeout);
+ const char *str_allow_blocking =
+ lttng_getenv("LTTNG_UST_ALLOW_BLOCKING");
+
+ if (str_allow_blocking) {
+ DBG("%s environment variable is set",
+ "LTTNG_UST_ALLOW_BLOCKING");
+ lttng_ust_ringbuffer_set_allow_blocking();
}
}
@@ -1698,7 +1687,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
timeout_mode = get_constructor_timeout(&constructor_timeout);
- get_blocking_retry_timeout();
+ get_allow_blocking();
ret = sem_init(&constructor_wait, 0, 0);
if (ret) {
diff --git a/libringbuffer/frontend.h b/libringbuffer/frontend.h
index a2f7459..2a9fd09 100644
--- a/libringbuffer/frontend.h
+++ b/libringbuffer/frontend.h
@@ -65,7 +65,8 @@ struct lttng_ust_shm_handle *channel_create(const struct
lttng_ust_lib_ring_buff
size_t subbuf_size, size_t num_subbuf,
unsigned int switch_timer_interval,
unsigned int read_timer_interval,
- const int *stream_fds, int nr_stream_fds);
+ const int *stream_fds, int nr_stream_fds,
+ int64_t blocking_timeout);
/*
* channel_destroy finalizes all channel's buffers, waits for readers to
diff --git a/libringbuffer/frontend_types.h b/libringbuffer/frontend_types.h
index bf4b418..629abcb 100644
--- a/libringbuffer/frontend_types.h
+++ b/libringbuffer/frontend_types.h
@@ -70,7 +70,13 @@ struct channel {
size_t priv_data_offset;
unsigned int nr_streams; /* Number of streams */
struct lttng_ust_shm_handle *handle;
- char padding[RB_CHANNEL_PADDING];
+ /* Extended options. */
+ union {
+ struct {
+ int32_t blocking_timeout_ms;
+ } s;
+ char padding[RB_CHANNEL_PADDING];
+ } u;
/*
* Associated backend contains a variable-length array. Needs to
* be last member.
diff --git a/libringbuffer/rb-init.h b/libringbuffer/rb-init.h
index eba087f..f36d4ec 100644
--- a/libringbuffer/rb-init.h
+++ b/libringbuffer/rb-init.h
@@ -22,6 +22,6 @@
*/
void lttng_fixup_ringbuffer_tls(void);
-void lttng_ust_ringbuffer_set_retry_timeout(int timeout);
+void lttng_ust_ringbuffer_set_allow_blocking(void);
#endif /* _LTTNG_UST_LIB_RINGBUFFER_RB_INIT_H */
diff --git a/libringbuffer/ring_buffer_frontend.c
b/libringbuffer/ring_buffer_frontend.c
index 9ecdc15..e19c22a 100644
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -151,12 +151,19 @@ 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;
+static bool lttng_ust_allow_blocking;
-void lttng_ust_ringbuffer_set_retry_timeout(int timeout)
+void lttng_ust_ringbuffer_set_allow_blocking(void)
{
- lttng_ust_blocking_retry_timeout = timeout;
+ lttng_ust_allow_blocking = true;
+}
+
+/* Get blocking timeout, in ms */
+static int lttng_ust_ringbuffer_get_timeout(struct channel *chan)
+{
+ if (!lttng_ust_allow_blocking)
+ return 0;
+ return chan->u.s.blocking_timeout_ms;
}
/**
@@ -951,7 +958,8 @@ struct lttng_ust_shm_handle *channel_create(const struct
lttng_ust_lib_ring_buff
void *buf_addr, size_t subbuf_size,
size_t num_subbuf, unsigned int switch_timer_interval,
unsigned int read_timer_interval,
- const int *stream_fds, int nr_stream_fds)
+ const int *stream_fds, int nr_stream_fds,
+ int64_t blocking_timeout)
{
int ret;
size_t shmsize, chansize;
@@ -959,6 +967,7 @@ struct lttng_ust_shm_handle *channel_create(const struct
lttng_ust_lib_ring_buff
struct lttng_ust_shm_handle *handle;
struct shm_object *shmobj;
unsigned int nr_streams;
+ int64_t blocking_timeout_ms;
if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
nr_streams = num_possible_cpus();
@@ -968,6 +977,16 @@ struct lttng_ust_shm_handle *channel_create(const struct
lttng_ust_lib_ring_buff
if (nr_stream_fds != nr_streams)
return NULL;
+ /* usec to msec */
+ if (blocking_timeout < 0) {
+ blocking_timeout_ms = -1;
+ } else {
+ blocking_timeout_ms = blocking_timeout / 1000;
+ if (blocking_timeout_ms != (int32_t) blocking_timeout_ms) {
+ return NULL;
+ }
+ }
+
if (lib_ring_buffer_check_config(config, switch_timer_interval,
read_timer_interval))
return NULL;
@@ -1021,6 +1040,8 @@ struct lttng_ust_shm_handle *channel_create(const struct
lttng_ust_lib_ring_buff
*priv_data = NULL;
}
+ chan->u.s.blocking_timeout_ms = (int32_t) blocking_timeout_ms;
+
ret = channel_backend_init(&chan->backend, name, config,
subbuf_size, num_subbuf, handle,
stream_fds);
@@ -2065,7 +2086,7 @@ 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;
+ int timeout_left_ms = lttng_ust_ringbuffer_get_timeout(chan);
retry:
offsets->begin = offset_cmp = v_read(config, &buf->offset);
--
2.1.4
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