On 5/15/25 12:16 AM, Jason Xing wrote:
> From: Jason Xing <[email protected]>
>
> In this version, only support dumping the counter for buffer full and
> implement the framework of how it works.
>
> Users can pass certain flag to fetch what field/statistics they expect
> to know. Each time it only returns one result. So do not pass multiple
> flags.
>
> Reviewed-by: Yushan Zhou <[email protected]>
> Signed-off-by: Jason Xing <[email protected]>
> ---
> v2
> 1. refactor relay_dump() and make it only return a pure size_t result
> of the value that users specifies.
> 2. revise the commit log.
> ---
> include/linux/relay.h | 7 +++++++
> kernel/relay.c | 31 +++++++++++++++++++++++++++++++
> 2 files changed, 38 insertions(+)
>
> diff --git a/include/linux/relay.h b/include/linux/relay.h
> index ce7a1b396872..3fb285716e34 100644
> --- a/include/linux/relay.h
> +++ b/include/linux/relay.h
> @@ -31,6 +31,12 @@
> /*
> * Relay buffer statistics dump
> */
> +enum {
> + RELAY_DUMP_BUF_FULL = (1 << 0),
> +
> + RELAY_DUMP_LAST = RELAY_DUMP_BUF_FULL,
> +};
> +
> struct rchan_buf_stats
> {
> unsigned int full_count; /* counter for buffer full */
> @@ -167,6 +173,7 @@ struct rchan *relay_open(const char *base_filename,
> void *private_data);
> extern void relay_close(struct rchan *chan);
> extern void relay_flush(struct rchan *chan);
> +extern size_t relay_dump(struct rchan *chan, int flags);
> extern void relay_subbufs_consumed(struct rchan *chan,
> unsigned int cpu,
> size_t consumed);
> diff --git a/kernel/relay.c b/kernel/relay.c
> index eb3f630f3896..f47fc750e559 100644
> --- a/kernel/relay.c
> +++ b/kernel/relay.c
> @@ -701,6 +701,37 @@ void relay_flush(struct rchan *chan)
> }
> EXPORT_SYMBOL_GPL(relay_flush);
>
> +/**
> + * relay_dump - dump channel buffer statistics
> + * @chan: the channel
> + * @flags: select particular information to dump
> + *
> + * Returns the count of certain field that caller specifies.
> + */
> +size_t relay_dump(struct rchan *chan, int flags)
> +{
> + unsigned int i, count = 0;
> + struct rchan_buf *rbuf;
> +
> + if (!chan || flags > RELAY_DUMP_LAST)
> + return 0;
> +
> + if (chan->is_global) {
> + rbuf = *per_cpu_ptr(chan->buf, 0);
> + if (flags & RELAY_DUMP_BUF_FULL)
> + count = rbuf->stats.full_count;
> + } else {
> + for_each_online_cpu(i) {
> + if ((rbuf = *per_cpu_ptr(chan->buf, i)))
> + if (flags & RELAY_DUMP_BUF_FULL)
> + count += rbuf->stats.full_count;
Kernel tends to avoid the rolled-into-one assignment and check, it's
easy to misread. This:
rbuf = *per_cpu_ptr(chan->buf, i);
if (rbuf && flags & RELAY_DUMP_BUF_FULL)
count += rbuf->stats.full_count;
reads much easier. IMHO.
--
Jens Axboe
