Messages in this thread | | | Date | Wed, 8 Jan 2020 15:35:22 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf report: Fix no libunwind compiled warning break s390 issue |
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On Wed, Jan 08, 2020 at 09:02:02PM +0800, Jin, Yao wrote: > > > On 1/8/2020 6:27 PM, Jiri Olsa wrote: > > On Wed, Jan 08, 2020 at 03:17:45AM +0800, Jin Yao wrote: > > > Commit 800d3f561659 ("perf report: Add warning when libunwind not compiled in") > > > breaks the s390 platform. S390 uses libdw-dwarf-unwind for call chain > > > unwinding and had no support for libunwind. > > > > > > So the warning "Please install libunwind development packages during the perf build." > > > caused the confusion even if the call-graph is displayed correctly. > > > > > > This patch adds checking for HAVE_DWARF_SUPPORT, which is set when > > > libdw-dwarf-unwind is compiled in. > > > > > > Fixes: 800d3f561659 ("perf report: Add warning when libunwind not compiled in") > > > > > > Reviewed-by: Thomas Richter <tmricht@linux.ibm.com> > > > Tested-by: Thomas Richter <tmricht@linux.ibm.com> > > > Signed-off-by: Jin Yao <yao.jin@linux.intel.com> > > > > perfect, I have the same change prepared for sending, but it's > > together with making libdw default dwarf unwinder, which I'm still > > not sure we want to do, so it all got posponed ;-) > > > would you guys be ok with that? with having libdw picked up as > default dwarf unwinder.. > > > > I've roughly compared the performance between libunwind-dev and libdw-dev. > While in my test (on KBL desktop), for the same perf report command-line, it > looks the perf built with libunwind-dev is much faster than the perf built > with libdw-dev.
ok, that's valid point.. the reason we start discussing it, was that libunwind does not seem to support compressed ELF debug sections, which works via libdw unwind
> > The command line is as following: > > perf record --call-graph dwarf ./div > perf report -g graph --stdio
I'll try to do some profiling and check with outr contact in libdw to comment/check on that
thanks, jirka
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