Commit 24b659a1 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt

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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent a0a4419e
...@@ -6,7 +6,7 @@ ...@@ -6,7 +6,7 @@
.globl vdso32_start, vdso32_end .globl vdso32_start, vdso32_end
.balign PAGE_SIZE .balign PAGE_SIZE
vdso32_start: vdso32_start:
.incbin "arch/powerpc/kernel/vdso32/vdso32.so" .incbin "arch/powerpc/kernel/vdso32/vdso32.so.dbg"
.balign PAGE_SIZE .balign PAGE_SIZE
vdso32_end: vdso32_end:
......
...@@ -6,7 +6,7 @@ ...@@ -6,7 +6,7 @@
.globl vdso64_start, vdso64_end .globl vdso64_start, vdso64_end
.balign PAGE_SIZE .balign PAGE_SIZE
vdso64_start: vdso64_start:
.incbin "arch/powerpc/kernel/vdso64/vdso64.so" .incbin "arch/powerpc/kernel/vdso64/vdso64.so.dbg"
.balign PAGE_SIZE .balign PAGE_SIZE
vdso64_end: vdso64_end:
......
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