Currently the PERF_EVENT_IOC_REFRESH ioctl, when applied to a group leader, will refresh all children. Also if a refresh value of 0 is chosen then the refresh becomes infinite (never runs out). Back in 2011 PAPI was relying on these behaviors but I was told that both were unsupported and subject to being removed at any time. (See https://lkml.org/lkml/2011/5/24/337 ) However the behavior has not been changed. This patch updates the manpage to still list the behavior as unsupported, but removes the innacurate description of it only being a problem with 2.6 kernels. Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 39c8d8c..76136e2 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -2353,6 +2353,12 @@ once the counter reaches 0 is indicated and the underlying event is disabled. +Refreshing an event group leader refreshes all siblings and +refreshing with a parameter of 0 currently enables infinite +refreshes; +these behaviors are unsupported and should not be relied on. +.\" See https://lkml.org/lkml/2011/5/24/337 + Starting with Linux 3.18, .\" commit 179033b3e064d2cd3f5f9945e76b0a0f0fbf4883 .B POLL_HUP @@ -2805,11 +2811,6 @@ Prior to Linux 2.6.35, .B PERF_FORMAT_GROUP did not work with attached processes. -In older Linux 2.6 versions, -refreshing an event group leader refreshed all siblings, -and refreshing with a parameter of 0 enabled infinite refresh. -This behavior is unsupported and should not be relied on. - There is a bug in the kernel code between Linux 2.6.36 and Linux 3.0 that ignores the "watermark" field and acts as if a wakeup_event -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
