Messages in this thread Patch in this message | | | Date | Thu, 7 Jan 2016 20:31:25 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH 1/8] perf: Add PERF_SAMPLE_PHYS_ADDR |
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On Thu, Jan 07, 2016 at 03:55:23PM +0000, Liang, Kan wrote: > > > > On Wed, Jan 06, 2016 at 06:04:30AM -0500, kan.liang@intel.com wrote: > > > From: Kan Liang <kan.liang@intel.com> > > > > > > For understanding how the workload maps to memory channels and > > > hardware behavior, it's useful to collect address maps with physical > > addresses. > > > This is not intended for detecting page sharing (which can be already > > > done using the mmap inode), but for lower level hardware behavior > > > studies. > > > Perf supports load latency/DLA which can only collect virtual addresses. > > > This patch add a new sample type PERF_SAMPLE_PHYS_ADDR to expose > > the > > > physical addresses. > > > For kernel direct mapping addresses, the patch uses virt_to_phys to > > > convert the virtual addresses from DLA to physical address. > > > For user virtual addresses, __get_user_pages_fast is used to walk the > > > pages tables for user physical address. > > > This does not work for vmalloc addresses. Right now these are not > > > resolved, but code to do that could be added. > > > For security, the physical address can only be exposed to root or > > > privileged user. > > > > > > Signed-off-by: Kan Liang <kan.liang@intel.com> > > > --- > > > arch/x86/kernel/cpu/perf_event.h | 2 +- > > > arch/x86/kernel/cpu/perf_event_intel_ds.c | 23 > > +++++++++++++++++++++++ > > > include/linux/perf_event.h | 3 +++ > > > include/uapi/linux/perf_event.h | 4 +++- > > > kernel/events/core.c | 11 +++++++++++ > > > 5 files changed, 41 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/x86/kernel/cpu/perf_event.h > > > b/arch/x86/kernel/cpu/perf_event.h > > > index 799e6bd..164de68 100644 > > > --- a/arch/x86/kernel/cpu/perf_event.h > > > +++ b/arch/x86/kernel/cpu/perf_event.h > > > @@ -90,7 +90,7 @@ struct amd_nb { > > > (PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_ADDR | \ > > > PERF_SAMPLE_ID | PERF_SAMPLE_CPU | > > PERF_SAMPLE_STREAM_ID | \ > > > PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_IDENTIFIER | \ > > > - PERF_SAMPLE_TRANSACTION) > > > + PERF_SAMPLE_TRANSACTION | PERF_SAMPLE_PHYS_ADDR) > > > > could you please add some probe code to detect kernel support, so we get > > some sensible error message > > > > I'm not quite sure what kind of probe code do you mean. > Yes, the error message below is not accurate. It could be some errors in > sample_type, read_format, branch_sample_type or something else. > Because they share the same error code -EINVAL. Perf tool cannot know > more. > I think we may print some error kernel messages when invalid attr is > detected. So the user can get more detail messages from dmesg. > > Or you want me to add some extra code to detect the kernel capability > before opening event? If so, I think we may do it in separate patches.
yep, could be done later
jirka
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