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| -rw-r--r-- | Documentation/libtraceevent-kbuffer-timestamp.txt | 208 |
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diff --git a/Documentation/libtraceevent-kbuffer-timestamp.txt b/Documentation/libtraceevent-kbuffer-timestamp.txt new file mode 100644 index 0000000..d7de225 --- /dev/null +++ b/Documentation/libtraceevent-kbuffer-timestamp.txt @@ -0,0 +1,208 @@ +libtraceevent(3) +================ + +NAME +---- +kbuffer_timestamp, kbuffer_subbuf_timestamp - +Functions that read various data of a kbuffer descriptor + +SYNOPSIS +-------- +[verse] +-- +*#include <kbuffer.h>* + +unsigned long long *kbuffer_timestamp*(struct kbuffer pass:[*]_kbuf_); +unsigned long long *kbuffer_subbuf_timestamp*(struct kbuffer pass:[*]_kbuf_, void pass:[*]_subbuf_); +-- + +DESCRIPTION +----------- +The function *kbuffer_timestamp()* returns the timestamp of the current event of _kbuf_. + +The function *kbuffer_subbuf_timestamp()* returns the timestamp for the sub-buffer +that was loaded in _kbuf_. This usually is (but not guaranteed to be) the timestamp +of the first event on the sub-buffer. + +The function *kbuffer_start_of_data()* returns the offset of where the delta + +RETURN VALUE +------------ +*kbuffer_read_event()* returns the event that the _kbuf_ descriptor is currently at, +or NULL if the last event was passed (by *kbuffer_next_event()*). + +*kbuffer_next_event()* returns the next event after the current event or NULL if there +are no more events. + +*kbuffer_read_at_offset()* returns the event at a given _offset_ from the start of +the sub-buffer stored in _kbuf_, or NULL if there exists no event. Note, _offset_ +only needs to be an offset that lands on the record, or is at the start of it. It does +not need to be exactly at the beginning of the record. + +*kbuffer_missed_events()* returns 0 if there were no missed events before loaded sub-buffer. +Returns -1 if there were an unknown number of missed events, or if the number of missed events +is known, that number will be returned. + +*kbuffer_event_size()* returns the size of the data payload of the current event of _kbuf_. + +*kbuffer_curr_size()* returns the size of the entire record of the current event of _kbuf_. +This includes the size of the meta data for that record. + +*kbuf_curr_offset()* returns the offset of the current record from the beginning of the _kbuf_ +sub-buffer. + +*kbuf_curr_index()* returns the index of the current record from the beginning of the _kbuf_ +data section. + +EXAMPLE +------- +[source,c] +-- +#include <stdio.h> +#include <stdlib.h> +#include <fcntl.h> +#include <unistd.h> +#include <sys/stat.h> + +#include <kbuffer.h> + +int main (int argc, char **argv) +{ + unsigned long long ts; + struct kbuffer *kbuf; + struct stat st; + char *buf; + void *event; + int save_offset = -1; + int record_size; + int offset; + int index; + int size; + int ret; + int fd; + int i = 0; + + if (argc < 2) { + printf("usage: %s raw-subbuffer-page\n", argv[0]); + printf(" Try: dd count=1 bs=4096 if=/sys/kernel/tracing/per_cpu/cpu0/trace_pipe_raw of=/tmp/file\n"); + exit(0); + } + + if (stat(argv[1], &st) < 0) { + perror("stat"); + exit(-1); + } + + buf = malloc(st.st_size); + if (!buf) { + perror("Allocating buffer"); + exit(-1); + } + + fd = open(argv[1], O_RDONLY); + if (fd < 0) { + perror(argv[1]); + exit(-1); + } + + ret = read(fd, buf, st.st_size); + if (ret < 0) { + perror("Reading buffer"); + exit(-1); + } + close(fd); + + kbuf = kbuffer_alloc(KBUFFER_ENDIAN_SAME_AS_HOST, + KBUFFER_LSIZE_SAME_AS_HOST); + if (!kbuf) { + perror("Creating kbuffer"); + exit(-1); + } + ret = kbuffer_load_subbuffer(kbuf, buf); + if (ret < 0) { + perror("Loading sub bufer"); + exit(-1); + } + + if (kbuffer_subbuffer_size(kbuf) > st.st_size) { + fprintf(stderr, "kbuffer is bigger than raw size %d > %ld\n", + kbuffer_subbuffer_size(kbuf), st.st_size); + exit(-1); + } + + ret = kbuffer_missed_events(kbuf); + if (ret) { + if (ret > 0) + printf("Missed %d events before this buffer\n", ret); + else + printf("Missed unknown number of events before this buffer\n"); + } + do { + event = kbuffer_read_event(kbuf, &ts); + if (event) { + record_size = kbuffer_curr_size(kbuf); + offset = kbuffer_curr_offset(kbuf); + index = kbuffer_curr_index(kbuf); + size = kbuffer_event_size(kbuf); + + if (i == 20) + save_offset = offset; + printf(" event %3d ts:%lld\trecord_size:%d size:%d\tindex:%d offset:%d\n", + i++, ts, record_size, size, index, offset); + event = kbuffer_next_event(kbuf, NULL); + } + } while (event); + + if (!event) + printf("Finished sub buffer\n"); + + if (save_offset > 0) { + event = kbuffer_read_at_offset(kbuf, save_offset, &ts); + if (!event) { + fprintf(stderr, "Funny, can't find event 20 at offset %d\n", save_offset); + exit(-1); + } + record_size = kbuffer_curr_size(kbuf); + offset = kbuffer_curr_offset(kbuf); + index = kbuffer_curr_index(kbuf); + size = kbuffer_event_size(kbuf); + + printf("\n saved event 20 ts:%lld\trecord_size:%d size:%d\tindex:%d offset:%d\n\n", + ts, record_size, size, index, offset); + } + kbuffer_free(kbuf); + + return 0; +} +-- +FILES +----- +[verse] +-- +*event-parse.h* + Header file to include in order to have access to the library APIs. +*-ltraceevent* + Linker switch to add when building a program that uses the library. +-- + +SEE ALSO +-------- +*libtraceevent*(3), *trace-cmd*(1) + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*. +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtraceevent is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/ |