Hi,
On Mon, May 09, 2016 at 05:22:15PM -0700, Shaohua Li wrote:
> if trace isn't enabled, parsing cgroup path just wastes cpu
>
> Signed-off-by: Shaohua Li <shli@xxxxxx>
> ---
> block/blk-throttle.c | 5 ++---
> include/linux/blktrace_api.h | 9 +++++++++
> 2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 2149a1d..47a3e54 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -211,15 +211,14 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
> *
> * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
> * throtl_grp; otherwise, just "throtl".
> - *
> - * TODO: this should be made a function and name formatting should happen
> - * after testing whether blktrace is enabled.
> */
> #define throtl_log(sq, fmt, args...) do { \
> struct throtl_grp *__tg = sq_to_tg((sq)); \
> struct throtl_data *__td = sq_to_td((sq)); \
> \
> (void)__td; \
> + if (likely(!blk_trace_note_message_enabled(__td->queue))) \
> + break; \
> if ((__tg)) { \
> char __pbuf[128]; \
> \
> diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
> index afc1343..0f3172b 100644
> --- a/include/linux/blktrace_api.h
> +++ b/include/linux/blktrace_api.h
> @@ -57,6 +57,14 @@ void __trace_note_message(struct blk_trace *, const char *fmt, ...);
> } while (0)
> #define BLK_TN_MAX_MSG 128
>
> +static inline bool blk_trace_note_message_enabled(struct request_queue *q)
> +{
> + struct blk_trace *bt = q->blk_trace;
> + if (likely(!bt))
> + return false;
> + return bt->act_mask & BLK_TC_NOTIFY;
> +}
Is there any reason to skip following condition?
if (unlikely(bt->trace_state != Blktrace_running &&
!blk_tracer_enabled))
Thanks,
- Simon
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