[...]
> +EXAMPLE
> +-------
> +[source,c]
> +--
> +#include <stdlib.h>
> +#include <ctype.h>
> +#include <tracefs.h>
> +
> +static void read_page(struct tep_handle *tep, struct kbuffer *kbuf)
read_subbuf?
> +{
> + static struct trace_seq seq;
> + struct tep_record record;
> +
> + if (seq.buffer)
> + trace_seq_reset(&seq);
> + else
> + trace_seq_init(&seq);
> +
> + while ((record.data = kbuffer_read_event(kbuf, &record.ts))) {
> + record.size = kbuffer_event_size(kbuf);
> + kbuffer_next_event(kbuf, NULL);
> + tep_print_event(tep, &seq, &record,
> + "%s-%d %9d\t%s: %s\n",
> + TEP_PRINT_COMM,
> + TEP_PRINT_PID,
> + TEP_PRINT_TIME,
> + TEP_PRINT_NAME,
> + TEP_PRINT_INFO);
> + trace_seq_do_printf(&seq);
> + trace_seq_reset(&seq);
> + }
> +}
> +
[...]
> +__hidden void *trace_mmap(int fd, struct kbuffer *kbuf)
> +{
> + struct trace_mmap *tmap;
> + int page_size;
> + void *meta;
> + void *data;
> +
> + page_size = getpagesize();
> + meta = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0);
> + if (meta == MAP_FAILED)
> + return NULL;
> +
> + tmap = calloc(1, sizeof(*tmap));
> + if (!tmap) {
> + munmap(meta, page_size);
> + return NULL;
> + }
> +
> + tmap->kbuf = kbuffer_dup(kbuf);
> + if (!tmap->kbuf) {
> + munmap(meta, page_size);
> + free(tmap);
> + }
> +
> + tmap->fd = fd;
> +
> + tmap->map = meta;
> + tmap->meta_len = tmap->map->meta_page_size;
> +
> + if (tmap->meta_len > page_size) {
> + munmap(meta, page_size);
> + meta = mmap(NULL, tmap->meta_len, PROT_READ, MAP_SHARED, fd, 0);
> + if (meta == MAP_FAILED) {
> + kbuffer_free(tmap->kbuf);
> + free(tmap);
> + return NULL;
> + }
> + tmap->map = meta;
> + }
> +
> + tmap->data_pages = meta + tmap->meta_len;
> +
> + tmap->data_len = tmap->map->subbuf_size * tmap->map->nr_subbufs;
> +
> + tmap->data = mmap(NULL, tmap->data_len, PROT_READ, MAP_SHARED,
> + fd, tmap->meta_len);
> + if (tmap->data == MAP_FAILED) {
> + munmap(meta, tmap->meta_len);
> + kbuffer_free(tmap->kbuf);
> + free(tmap);
> + return NULL;
> + }
> +
> + tmap->last_idx = tmap->map->reader.id;
> +
> + data = tmap->data + tmap->map->subbuf_size * tmap->last_idx;
> + kbuffer_load_subbuffer(kbuf, data);
Could it fast-forward to the event until tmap->map->reader.read? So we don't
read again the same events.
Something like
while (kbuf->curr < tmap->map->reader.read)
kbuffer_next_event(kbuf, NULL);
> +
> + return tmap;
> +}
> +
> +__hidden void trace_unmap(void *mapping)
> +{
> + struct trace_mmap *tmap = mapping;
> +
> + munmap(tmap->data, tmap->data_len);
> + munmap(tmap->map, tmap->meta_len);
> + kbuffer_free(tmap->kbuf);
> + free(tmap);
> +}
> +
> +__hidden int trace_mmap_load_subbuf(void *mapping, struct kbuffer *kbuf)
> +{
> + struct trace_mmap *tmap = mapping;
> + void *data;
> + int id;
> +
> + id = tmap->map->reader.id;
> + data = tmap->data + tmap->map->subbuf_size * id;
> +
> + /*
> + * If kbuf doesn't point to the current sub-buffer
> + * just load it and return.
> + */
> + if (data != kbuffer_subbuffer(kbuf)) {
> + kbuffer_load_subbuffer(kbuf, data);
> + return 1;
> + }
> +
> + /*
> + * Perhaps the reader page had a write that added
> + * more data.
> + */
> + kbuffer_refresh(kbuf);
> +
> + /* Are there still events to read? */
> + if (kbuffer_curr_size(kbuf))
> + return 1;
It does not seem to be enough, only kbuf->size is updated in kbuffer_refresh()
while kbuffer_curr_size is next - cur.
> +
> + /* See if a new page is ready? */
> + if (ioctl(tmap->fd, TRACE_MMAP_IOCTL_GET_READER) < 0)
> + return -1;
Maybe this ioctl should be called regardless if events are found on the current
reader page. This would at least update the reader->read field and make sure
subsequent readers are not getting the same events we already had here?
> + id = tmap->map->reader.id;
> + data = tmap->data + tmap->map->subbuf_size * id;
> +
[...]
|