Support to dump the kernel metadata cache from the beginning

On demand, the consumer can ask for the kernel tracer to dump the
content of the metadata cache (depends on lttng-modules 2.11). This
allows to extract the exact same metadata (compared to regenerating it
which could change the epoch offset).

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/kernel-ctl/kernel-ctl.c b/src/common/kernel-ctl/kernel-ctl.c
index 6a256fefd00fa06b107c61aff78ea09151e63627..a495ca9b705bee48c94d7d32c9b602cbc9a48a7f 100644 (file)
--- a/src/common/kernel-ctl/kernel-ctl.c
+++ b/src/common/kernel-ctl/kernel-ctl.c
@@ -419,6 +419,10 @@ int kernctl_get_metadata_version(int fd, uint64_t *version)
        return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_METADATA_VERSION, version);
 }
 
+int kernctl_metadata_cache_dump(int fd)
+{
+       return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_METADATA_CACHE_DUMP);
+}
 
 /* Buffer operations */
 

diff --git a/src/common/kernel-ctl/kernel-ctl.h b/src/common/kernel-ctl/kernel-ctl.h
index d88f5e7659f336dcf8794b5684f624ad1dfb9212..fbb273190cf56aaf8477c75fb8161128de977efb 100644 (file)
--- a/src/common/kernel-ctl/kernel-ctl.h
+++ b/src/common/kernel-ctl/kernel-ctl.h
@@ -95,6 +95,7 @@ int kernctl_put_subbuf(int fd);
 int kernctl_buffer_flush(int fd);
 int kernctl_buffer_flush_empty(int fd);
 int kernctl_get_metadata_version(int fd, uint64_t *version);
+int kernctl_metadata_cache_dump(int fd);
 
 /* index */
 int kernctl_get_timestamp_begin(int fd, uint64_t *timestamp_begin);

diff --git a/src/common/kernel-ctl/kernel-ioctl.h b/src/common/kernel-ctl/kernel-ioctl.h
index 3c4f4129e63c8c0129521ca9ad617599927a3ce3..4ab0eabbc140f757e9af4aedb15ef43b25458536 100644 (file)
--- a/src/common/kernel-ctl/kernel-ioctl.h
+++ b/src/common/kernel-ctl/kernel-ioctl.h
@@ -59,6 +59,11 @@
 #define RING_BUFFER_SNAPSHOT_SAMPLE_POSITIONS  _IO(0xF6, 0x0E)
 /* Flush the current sub-buffer, even if empty. */
 #define RING_BUFFER_FLUSH_EMPTY                        _IO(0xF6, 0x0F)
+/*
+ * Reset the position of what has been consumed from the metadata cache to 0
+ * so it can be read again.
+ */
+#define RING_BUFFER_METADATA_CACHE_DUMP        _IO(0xF6, 0x10)
 
 /* returns the timestamp begin of the current sub-buffer */
 #define LTTNG_RING_BUFFER_GET_TIMESTAMP_BEGIN     _IOR(0xF6, 0x20, uint64_t)