Messages in this thread | | | From | Namhyung Kim <> | Subject | Re: [PATCH 2/3] perf symbol: Implement a very simple ELF symbol parser | Date | Mon, 17 Nov 2014 11:31:10 +0900 |
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On Mon, 10 Nov 2014 09:09:04 -0300, Arnaldo Carvalho de Melo wrote: > Em Mon, Nov 10, 2014 at 03:36:48PM +0900, Namhyung Kim escreveu: >> Hi Arnaldo, >> >> On Fri, 7 Nov 2014 12:26:18 -0300, Arnaldo Carvalho de Melo wrote: >> > Em Fri, Nov 07, 2014 at 02:20:05PM +0900, Namhyung Kim escreveu: >> >> It'll be used to show (userspace) symbol names when libelf isn't (or >> >> cannot be) linked. >> > >> > Does this deals with prelink, etc? >> >> I believe so. :) >> >> > >> >> # Overhead Command Shared Object Symbol >> >> # ........ .......... ................. ......................... >> >> # >> >> 37.01% mem-memcpy libc-2.17.so [.] __memcpy_ssse3_back >> >> namhyung@sejong:linux$ readelf -WS /lib64/libc-2.17.so | grep prelink >> [41] .gnu.prelink_undo PROGBITS 0000000000000000 200368 000c30 01 0 0 8 >> >> namhyung@sejong:linux$ nm /lib64/libc-2.17.so | grep __memcpy_ssse3_back >> 0000003153f46f40 t __memcpy_ssse3_back > > Right, in this case most of the samples seems to map to what is expected > for that workload, and the binary was prelinked. Good. > > What about binaries that are not prelinked? IIRC there is code in the > full blown ELF symbol-elf.c file to detect that and act accordingly, > from a _very_ quick look I didn't saw it in this minimalistic ELF symtab > reader, hence my question.
AFAIK we deal with prelink'ed binary and normal binary as same way - we only cares about the file offsets.
$ perf top --stdio PerfTop: 110 irqs/sec kernel:70.0% exact: 0.0% [4000Hz cycles], (all, 12 CPUs) -------------------------------------------------------------------------------------------- 9.42% perf [.] map__process_kallsym_symbol 8.91% [kernel] [k] kallsyms_expand_symbol.constprop.1 6.80% [kernel] [k] memcpy 6.08% [kernel] [k] vsnprintf ...
Thanks, Namhyung
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