Em Mon, Nov 05, 2012 at 02:50:47PM +0100, Stephane Eranian escreveu:
> Or if one is interested in the data view:
> $ perf mem -t load rep --sort=symbol_daddr,cost
> # Samples: 19K of event 'cpu/mem-loads/pp'
> # Total cost : 1013994
> # Sort order : symbol_daddr,cost
> #
> # Overhead Samples Data Symbol Cost
> # ........ ........... ...................... .......
> #
> 0.10% 1 [.] 0x00007f67dffe8038 986
> 0.09% 1 [.] 0x00007f67df91a750 890
> 0.08% 1 [.] 0x00007f67e288fba8 826
>
> CAVEAT: Note that the data addresses are not resolved correctly currently due
> to a
> problem in perf data symbol resolution code which I have not been able to
> uncover so far.
Stephane,
Those data addresses mostly are on the stack, we need reverse
resolution using DWARF location expressions to figure out what is the
name of a variable that is on a particular address, etc.
Masami, have you played with this already? I mean:
[root@sandy acme]# perf mem -t load rep --stdio --sort=symbol,symbol_daddr,cost
# Samples: 30 of event 'cpu/mem-loads/pp'
# Total cost : 640
# Sort order : symbol,symbol_daddr,cost
#
# Overhead Samples Symbol Data Symbol Cost
# ........ ........... ...................... ...................... .......
#
55.00% 1 [k] lookup_fast [k] 0xffff8803b7521bd4 352
5.47% 1 [k] cache_alloc_refill [k] 0xffff880407705024 35
3.44% 1 [k] cache_alloc_refill [k] 0xffff88041d8527d8 22
3.28% 1 [k] run_timer_softirq [k] 0xffff88041e2c3e90 21
2.50% 1 [k] __list_add [k] 0xffff8803b7521d68 16
2.19% 1 [.] __strcoll_l [.] 0x00007fffa8d44080 14
1.88% 1 [.] __strcoll_l [.] 0x00007fffa8d44104 12
If we go to the annotation browser to see where is that lookup_fast hitting we
get:
100.00 │ mov -0x34(%rbp),%eax
How to map 0xffff8803b7521bd4 to a stack variable, struct members and all?
Humm, for userspace we have PERF_SAMPLE_REGS_USER for the dwarf unwinder we
need for userspace, but what about reverse mapping of kernel variables? Jiri?
- Arnaldo
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