Instead of having a PERF_EVENT_IOC_FLUSH ioctl this instead allows userspace to use fsync for flushing pmu samples, as suggested by Ingo Molnar - thanks.
For reference I've also pushed a patch to my Mesa branch to test this: https://github.com/rib/mesa wip/rib/oa-hsw-4.0.0
- Robert
--- >8 ---
To allow for pmus that may have internal buffering (e.g. the hardware writes out data to a circular buffer which is only periodically forwarded to userspace via perf) this enables userspace to explicitly ensure it has received all samples before a point in time.
Signed-off-by: Robert Bragg robert@sixbynine.org --- include/linux/perf_event.h | 7 +++++++ kernel/events/core.c | 23 +++++++++++++++++++++++ 2 files changed, 30 insertions(+)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 04e98c8..d7fac05 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -305,6 +305,13 @@ struct pmu { * Free pmu-private AUX data structures */ void (*free_aux) (void *aux); /* optional */ + + /* + * Flush buffered samples (E.g. for pmu hardware that writes samples to + * some intermediate buffer) userspace may need to explicitly ensure + * such samples have been forwarded to perf. + */ + int (*flush) (struct perf_event *event); /*optional */ };
/** diff --git a/kernel/events/core.c b/kernel/events/core.c index 2ba89a1..a604e0c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4728,6 +4728,28 @@ static int perf_fasync(int fd, struct file *filp, int on) return 0; }
+static int perf_fsync(struct file *filp, loff_t start, loff_t end, int datasync) +{ + struct perf_event *event = filp->private_data; + struct perf_event_context *ctx; + int ret; + + /* We don't have a use for synchonizing a specific range, or datasync + * but lets not silently ignore them in case we think of uses later... + */ + if (start != 0 || end != LLONG_MAX || datasync != 0) + return -EINVAL; + + if (!event->pmu->flush) + return 0; + + ctx = perf_event_ctx_lock(event); + ret = event->pmu->flush(event); + perf_event_ctx_unlock(event, ctx); + + return ret; +} + static const struct file_operations perf_fops = { .llseek = no_llseek, .release = perf_release, @@ -4737,6 +4759,7 @@ static const struct file_operations perf_fops = { .compat_ioctl = perf_compat_ioctl, .mmap = perf_mmap, .fasync = perf_fasync, + .fsync = perf_fsync, };
/*