Hi Stephane (and Jiri), Would you be willing to review/comment on Vince's patch, please.
Cheers, Michael On 02/12/2015 06:33 AM, Vince Weaver wrote: > > This manpage patch relates to the addition of PERF_SAMPLE_REGS_INTR > support added in the following commit: > > perf_sample_regs_intr; Linux 3.19 > commit 60e2364e60e86e81bc6377f49779779e6120977f > Author: Stephane Eranian <eran...@google.com> > > perf: Add ability to sample machine state on interrupt > > Reviewed-by: Jiri Olsa <jo...@redhat.com> > Signed-off-by: Stephane Eranian <eran...@google.com> > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> > Cc: cebbert.l...@gmail.com > Cc: Arnaldo Carvalho de Melo <a...@kernel.org> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: linux-...@vger.kernel.org > Link: > http://lkml.kernel.org/r/1411559322-16548-2-git-send-email-eran...@google.com > Signed-off-by: Ingo Molnar <mi...@kernel.org> > >>From what I can tell the primary difference between > PERF_SAMPLE_REGS_INTR and the existing PERF_SAMPLE_REGS_USER > is that the new support will return kernel register values > (I assume that's not some sort of info leak?). > > In theory also when precise_ip is set high enough you should > get the PEBS register state rather than the PMU interrupt > register state, but I was unable to construct a test case > on a Haswell system where I got different values with > precise_ip=0, precise_ip=2, or by using PERF_SAMPLE_REGS_USER > instead. Am I missing something about how to use this new > interface? > > Signed-off-by: Vince Weaver <vincent.wea...@maine.edu> > > diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 > index 39c8d8c..ca03928 100644 > --- a/man2/perf_event_open.2 > +++ b/man2/perf_event_open.2 > @@ -256,7 +256,7 @@ struct perf_event_attr { > __u32 sample_stack_user; /* size of stack to dump on > samples */ > __u32 __reserved_2; /* Align to u64 */ > - > + __u64 sample_regs_intr; /* regs to dump on samples */ > }; > .fi > .in > @@ -350,6 +350,11 @@ and > .I sample_stack_user > in Linux 3.7. > .\" commit 1659d129ed014b715b0b2120e6fd929bdd33ed03 > +.B PERF_ATTR_SIZE_VER4 > +is 104 corresponding to the addition of > +.I sample_regs_intr > +in Linux 3.19. > +.\" commit 60e2364e60e86e81bc6377f49779779e6120977f > .TP > .I "config" > This specifies which event you want, in conjunction with > @@ -752,6 +757,23 @@ event must be measured or no values will be recorded. > Also note that some perf_event measurements, such as sampled > cycle counting, may cause extraneous aborts (by causing an > interrupt during a transaction). > +.TP > +.BR PERF_SAMPLE_REGS_INTR " (since Linux 3.19)" > +.\" commit 60e2364e60e86e81bc6377f49779779e6120977f > +Records a subset of the current CPU register state > +as specified by > +.IR sample_regs_intr . > +Unlike > +.B PERF_SAMPLE_REGS_USER > +the register values will return kernel register > +state if the overflow happened while kernel > +code is running. > +If the CPU supports hardware sampling of > +register state (as does PEBS on x86) and > +.I precise_ip > +is set higher than zero then the register > +values returned are those captured by > +hardware. > .RE > .TP > .IR "read_format" > @@ -1855,6 +1877,9 @@ struct { > u64 weight; /* if PERF_SAMPLE_WEIGHT */ > u64 data_src; /* if PERF_SAMPLE_DATA_SRC */ > u64 transaction;/* if PERF_SAMPLE_TRANSACTION */ > + u64 abi; /* if PERF_SAMPLE_REGS_INTR */ > + u64 regs[weight(mask)]; > + /* if PERF_SAMPLE_REGS_INTR */ > }; > .fi > .RS 4 > @@ -2242,6 +2267,27 @@ the high 32 bits of the field by shifting right by > .B PERF_TXN_ABORT_SHIFT > and masking with > .BR PERF_TXN_ABORT_MASK . > +.TP > +.IR abi ", " regs[weight(mask)] > +If > +.B PERF_SAMPLE_REGS_INTR > +is enabled, then the user CPU registers are recorded. > + > +The > +.I abi > +field is one of > +.BR PERF_SAMPLE_REGS_ABI_NONE ", " PERF_SAMPLE_REGS_ABI_32 " or " > +.BR PERF_SAMPLE_REGS_ABI_64 . > + > +The > +.I regs > +field is an array of the CPU registers that were specified by > +the > +.I sample_regs_intr > +attr field. > +The number of values is the number of bits set in the > +.I sample_regs_intr > +bit mask. > .RE > .TP > .B PERF_RECORD_MMAP2 > > -- 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-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
