powerpc: Use unstripped VDSO image for more accurate profiling data

We are seeing a lot of hits in the VDSO that are not resolved by perf.
A while(1) gettimeofday() loop shows the issue:

27.64%  [vdso]  [.] 0x000000000000060c
22.57%  [vdso]  [.] 0x0000000000000628
16.88%  [vdso]  [.] 0x0000000000000610
12.39%  [vdso]  [.] __kernel_gettimeofday
 6.09%  [vdso]  [.] 0x00000000000005f8
 3.58%  test    [.] 00000037.plt_call.gettimeofday@@GLIBC_2.18
 2.94%  [vdso]  [.] __kernel_datapage_offset
 2.90%  test    [.] main

We are using a stripped VDSO image which means only symbols with
relocation info can be resolved. There isn't a lot of point to
stripping the VDSO, the debug info is only about 1kB:

4680 arch/powerpc/kernel/vdso64/vdso64.so
5815 arch/powerpc/kernel/vdso64/vdso64.so.dbg

By using the unstripped image, we can resolve all the symbols in the
VDSO and the perf profile data looks much better:

76.53%  [vdso]  [.] __do_get_tspec
12.20%  [vdso]  [.] __kernel_gettimeofday
 5.05%  [vdso]  [.] __get_datapage
 3.20%  test    [.] main
 2.92%  test    [.] 00000037.plt_call.gettimeofday@@GLIBC_2.18

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/vdso32/vdso32_wrapper.S b/arch/powerpc/kernel/vdso32/vdso32_wrapper.S
index 79683d0393f5d01577503b02d7d298018647a758..6ac107ac402a93ffcabb5f0cd365132f922fe88d 100644 (file)
--- a/arch/powerpc/kernel/vdso32/vdso32_wrapper.S
+++ b/arch/powerpc/kernel/vdso32/vdso32_wrapper.S
@@ -6,7 +6,7 @@
        .globl vdso32_start, vdso32_end
        .balign PAGE_SIZE
 vdso32_start:
-       .incbin "arch/powerpc/kernel/vdso32/vdso32.so"
+       .incbin "arch/powerpc/kernel/vdso32/vdso32.so.dbg"
        .balign PAGE_SIZE
 vdso32_end:
 

diff --git a/arch/powerpc/kernel/vdso64/vdso64_wrapper.S b/arch/powerpc/kernel/vdso64/vdso64_wrapper.S
index 8df9e2463007c1601012aae7062c6a8896ebf9ef..df60fca6a13d1eb745612e78c0be86a32fb78c45 100644 (file)
--- a/arch/powerpc/kernel/vdso64/vdso64_wrapper.S
+++ b/arch/powerpc/kernel/vdso64/vdso64_wrapper.S
@@ -6,7 +6,7 @@
        .globl vdso64_start, vdso64_end
        .balign PAGE_SIZE
 vdso64_start:
-       .incbin "arch/powerpc/kernel/vdso64/vdso64.so"
+       .incbin "arch/powerpc/kernel/vdso64/vdso64.so.dbg"
        .balign PAGE_SIZE
 vdso64_end: