On 02/12/2015 06:14 PM, Vince Weaver wrote: > > 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. Thanks, Vince. Applied. Cheers, Michael > 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 > > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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
