[ltt-dev] [PATCH 09/13] enable accessing struct ltt_channel_buf_struct

[Mathieu Desnoyers]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> 
> struct ltt_channel_buf_struct in ltt-relay.c and ltt-relay-locked.c
> are different to each other, we implement access-ops for access them.
> 

OK, as long as we don't use them in the write-side (this abstraction
adds a function call). Maybe we should document its purpose along with
this performance limitation.

Mathieu

> Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
> ---
>  b/ltt/ltt-relay-locked.c     |   18 ++++++++++++++++++
>  b/ltt/ltt-relay.c            |   18 ++++++++++++++++++
>  include/linux/ltt-channels.h |    7 +++++++
>  3 files changed, 43 insertions(+)
> diff --git a/include/linux/ltt-channels.h b/include/linux/ltt-channels.h
> index 4a3924b..db513cb 100644
> --- a/include/linux/ltt-channels.h
> +++ b/include/linux/ltt-channels.h
> @@ -45,11 +48,18 @@ struct ltt_channel_struct {
>  	void (*buffer_end) (struct rchan_buf *buf,
>  			u64 tsc, unsigned int offset, unsigned int subbuf_idx);
>  	struct kref kref;	/* Channel transport reference count */
> +	struct ltt_channel_buf_access_ops *buf_access_ops;
>  	unsigned int subbuf_size;
>  	unsigned int subbuf_cnt;
>  	const char *channel_name;
>  } ____cacheline_aligned;
>  
> +/* ops for accessing struct ltt_channel_struct.buf's data */
> +struct ltt_channel_buf_access_ops {
> +	unsigned long (*get_offset)(void *buf, int cpu);
> +	unsigned long (*get_consumed)(void *buf, int cpu);
> +};
> +
>  struct ltt_channel_setting {
>  	unsigned int subbuf_size;
>  	unsigned int subbuf_cnt;
> diff --git a/ltt/ltt-relay.c b/ltt/ltt-relay.c
> index 6d222c6..806558f
> --- a/ltt/ltt-relay.c
> +++ b/ltt/ltt-relay.c
> @@ -90,6 +90,24 @@ struct ltt_channel_buf_struct {
>  	atomic_t wakeup_readers;	/* Boolean : wakeup readers waiting ? */
>  } ____cacheline_aligned;
>  
> +static unsigned long get_offset(void *buf, int cpu)
> +{
> +	struct ltt_channel_buf_struct *ltt_buf = percpu_ptr(buf, cpu);
> +	return local_read(&ltt_buf->offset);
> +}
> +
> +static unsigned long get_consumed(void *buf, int cpu)
> +{
> +	struct ltt_channel_buf_struct *ltt_buf = percpu_ptr(buf, cpu);
> +	return atomic_long_read(&ltt_buf->consumed);
> +}
> +
> +static struct ltt_channel_buf_access_ops ltt_channel_buf_accesser =
> +{
> +	.get_offset   = get_offset,
> +	.get_consumed = get_consumed,
> +};
> +
>  /*
>   * Last TSC comparison functions. Check if the current TSC overflows
>   * LTT_TSC_BITS bits from the last TSC read. Reads and writes last_tsc
> diff --git a/ltt/ltt-relay-locked.c b/ltt/ltt-relay-locked.c
> index ef5f47c..a3c5bb9
> --- a/ltt/ltt-relay-locked.c
> +++ b/ltt/ltt-relay-locked.c
> @@ -81,6 +81,24 @@ struct ltt_channel_buf_struct {
>  	int wakeup_readers;		/* Boolean : wakeup readers waiting ? */
>  } ____cacheline_aligned;
>  
> +static unsigned long get_offset(void *buf, int cpu)
> +{
> +	struct ltt_channel_buf_struct *ltt_buf = percpu_ptr(buf, cpu);
> +	return ltt_buf->offset;
> +}
> +
> +static unsigned long get_consumed(void *buf, int cpu)
> +{
> +	struct ltt_channel_buf_struct *ltt_buf = percpu_ptr(buf, cpu);
> +	return ltt_buf->consumed;
> +}
> +
> +static struct ltt_channel_buf_access_ops ltt_channel_buf_accesser =
> +{
> +	.get_offset   = get_offset,
> +	.get_consumed = get_consumed,
> +};
> +
>  /*
>   * Last TSC comparison functions. Check if the current TSC overflows
>   * LTT_TSC_BITS bits from the last TSC read. Reads and writes last_tsc
> 
> 
> 
> 
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-- 
Mathieu Desnoyers
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