Messages in this thread Patch in this message | | | Subject | Re: [PATCH V2 01/13] perf/core: Add new branch sample type for LBR TOS | From | "Liang, Kan" <> | Date | Tue, 22 Oct 2019 11:39:28 -0400 |
| |
On 10/22/2019 5:39 AM, Peter Zijlstra wrote: > On Mon, Oct 21, 2019 at 01:03:02PM -0700, kan.liang@linux.intel.com wrote: >> From: Kan Liang <kan.liang@linux.intel.com> >> >> In LBR call stack mode, the depth of reconstructed LBR call stack limits >> to the number of LBR registers. With LBR Top-of-Stack (TOS) information, >> perf tool may stitch the stacks of two samples. The reconstructed LBR >> call stack can break the HW limitation. >> >> Add a new branch sample type to retrieve LBR TOS. >> >> Only when the new branch sample type is set, the TOS information is >> dumped into the PERF_SAMPLE_BRANCH_STACK output. >> Perf tool should check the attr.branch_sample_type, and apply the >> corresponding format for PERF_SAMPLE_BRANCH_STACK samples. >> Otherwise, some user case may be broken. For example, users may parse a >> perf.data, which include the new branch sample type, with an old version >> perf tool (without the check). Users probably get incorrect information >> without any warning. >> >> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> >> --- >> include/linux/perf_event.h | 4 ++++ >> include/uapi/linux/perf_event.h | 10 +++++++++- >> kernel/events/core.c | 10 ++++++++++ >> 3 files changed, 23 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h >> index 61448c19a132..0cebc8ec44fa 100644 >> --- a/include/linux/perf_event.h >> +++ b/include/linux/perf_event.h >> @@ -972,6 +972,10 @@ struct perf_sample_data { >> u64 stack_user_size; >> >> u64 phys_addr; >> + >> + /* PMU specific data */ >> + u64 lbr_tos; >> + >> } ____cacheline_aligned; > > Last time you put this in perf_branch_stack, that was a much better > place. Can't this work now?
It should still work. I just thought perf_branch_stack is a generic structure for branches. TOS is Intel specific for LBR call stack. Maybe it's better to move it out. Also, I wanted to make it consistent as perf tool struct branch_stack. But those should not be big deals.
I will move tos to perf_branch_stack in V3 as below.
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 0cebc8ec44fa..c8bf40e608b6 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -92,6 +92,7 @@ struct perf_raw_record { /* * branch stack layout: * nr: number of taken branches stored in entries[] + * tos: Top-of-Stack (TOS) information. PMU specific data. * * Note that nr can vary from sample to sample * branches (to, from) are stored from most recent @@ -100,6 +101,7 @@ struct perf_raw_record { */ struct perf_branch_stack { __u64 nr; + __u64 tos; /* PMU specific data */ struct perf_branch_entry entries[0]; };
Thanks, Kan
| |