On 07/12/13 23:22, Vince Weaver wrote: > > It turns out PERF_IOC_FLAG_GROUP was broken from > 75f937f24bd9 (in Linux 2.6.31, the initial perf_event release) > until 724b6daa1 (Linux 3.4). > > I've done some extensive kernel source code digging plus running tests of > various kernels and I hope the info presented is accurate now. > > Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx> Thanks, Vince. Applied. Cheers, Michael > diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 > index 504e801..ff7e4af 100644 > --- a/man2/perf_event_open.2 > +++ b/man2/perf_event_open.2 > @@ -1803,7 +1803,8 @@ file descriptor argument. > If the > .B PERF_IOC_FLAG_GROUP > bit is set in the ioctl argument, then all events in a group are > -enabled, even if the event specified is not the group leader. > +enabled, even if the event specified is not the group leader > +(note this flag was broken until Linux 3.4). > .TP > .B PERF_EVENT_IOC_DISABLE > Disables the individual counter or event group specified by the > @@ -1819,7 +1820,8 @@ stops that counter from counting but doesn't affect any other counter. > If the > .B PERF_IOC_FLAG_GROUP > bit is set in the ioctl argument, then all events in a group are > -disabled, even if the event specified is not the group leader. > +disabled, even if the event specified is not the group leader > +(note this flag was broken until Linux 3.4). > .TP > .B PERF_EVENT_IOC_REFRESH > Non-inherited overflow counters can use this > @@ -1848,14 +1850,9 @@ values. > If the > .B PERF_IOC_FLAG_GROUP > bit is set in the ioctl argument, then all events in a group are > -reset, even if the event specified is not the group leader. > +reset, even if the event specified is not the group leader > +(note this flag was broken until Linux 3.4). > > -If the > -.B PERF_IOC_FLAG_GROUP > -bit is not set, then the behavior is somwhat unexpected: > -when sent to a group leader only the leader is reset > -(children are left alone); > -when sent to a child all events in a group are reset. > .TP > .B PERF_EVENT_IOC_PERIOD > IOC_PERIOD is the command to update the period; it > @@ -2042,6 +2039,12 @@ Linux 2.6.36 and Linux 3.0 that ignores the > was chosen if the union has a > non-zero value in it. > > +From Linux 2.6.31 to Linux 3.4 the > +.B PERF_IOC_FLAG_GROUP > +ioctl argument was broken and would repeatedly operate > +on the event specified rather than iterating across > +all sibling events in a group. > + > Always double-check your results! > Various generalized events have had wrong values. > For example, retired branches measured > -- 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
