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SubjectRe: [RFC] perf: need to expose sched_clock to correlate user samples with kernel samples
On 2/1/13 7:18 AM, Pawel Moll wrote:
> 8<---
> From 2ad51a27fbf64bf98cee190efc3fbd7002819692 Mon Sep 17 00:00:00 2001
> From: Pawel Moll <pawel.moll@arm.com>
> Date: Fri, 1 Feb 2013 14:03:56 +0000
> Subject: [PATCH] perf: Add ioctl to return current time value
>
> To co-relate user space events with the perf events stream
> a current (as in: "what time(stamp) is it now?") time value
> must be made available.
>
> This patch adds a perf ioctl that makes this possible.

Are there any objections to this approach? I need a solution for my
time-of-day patch as well.

David

>
> Signed-off-by: Pawel Moll <pawel.moll@arm.com>
> ---
> include/uapi/linux/perf_event.h | 1 +
> kernel/events/core.c | 8 ++++++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 4f63c05..b745fb0 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -316,6 +316,7 @@ struct perf_event_attr {
> #define PERF_EVENT_IOC_PERIOD _IOW('$', 4, __u64)
> #define PERF_EVENT_IOC_SET_OUTPUT _IO ('$', 5)
> #define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
> +#define PERF_EVENT_IOC_GET_TIME _IOR('$', 7, __u64)
>
> enum perf_event_ioc_flags {
> PERF_IOC_FLAG_GROUP = 1U << 0,
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 301079d..4202b1c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3298,6 +3298,14 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> case PERF_EVENT_IOC_SET_FILTER:
> return perf_event_set_filter(event, (void __user *)arg);
>
> + case PERF_EVENT_IOC_GET_TIME:
> + {
> + u64 time = perf_clock();
> + if (copy_to_user((void __user *)arg, &time, sizeof(time)))
> + return -EFAULT;
> + return 0;
> + }
> +
> default:
> return -ENOTTY;
> }
>



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