linux-kernel - Re: [PATCH v1] perf record: collect user registers set jointly with dwarf stacks

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Date:   Wed, 17 Apr 2019 09:39:52 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] perf record: collect user registers set jointly with
 dwarf stacks

On Mon, Apr 15, 2019 at 06:36:13PM +0300, Alexey Budankov wrote:
> 
> When dwarf stacks are collected jointly with user specified register
> set using --user-regs option like below the full register context is
> still captured on a sample:
> 
>   $ perf record -g --call-graph dwarf,1024 --user-regs=IP,SP,BP -- matrix.gcc.g.O3
> 
>   188143843893585 0x6b48 [0x4f8]: PERF_RECORD_SAMPLE(IP, 0x4002): 23828/23828: 0x401236 period: 1363819 addr: 0x7ffedbdd51ac
>   ... FP chain: nr:0
>   ... user regs: mask 0xff0fff ABI 64-bit
>   .... AX    0x53b
>   .... BX    0x7ffedbdd3cc0
>   .... CX    0xffffffff
>   .... DX    0x33d3a
>   .... SI    0x7f09b74c38d0
>   .... DI    0x0
>   .... BP    0x401260
>   .... SP    0x7ffedbdd3cc0
>   .... IP    0x401236
>   .... FLAGS 0x20a
>   .... CS    0x33
>   .... SS    0x2b
>   .... R8    0x7f09b74c3800
>   .... R9    0x7f09b74c2da0
>   .... R10   0xfffffffffffff3ce
>   .... R11   0x246
>   .... R12   0x401070
>   .... R13   0x7ffedbdd5db0
>   .... R14   0x0
>   .... R15   0x0
>   ... ustack: size 1024, offset 0xe0
>    . data_src: 0x5080021
>    ... thread: stack_test2.g.O:23828
>    ...... dso: /root/abudanko/stacks/stack_test2.g.O3
> 
> After applying the change suggested in the patch the sample data contain
> only user specified register values:
> 
>   $ perf record -g --call-graph dwarf,1024 --user-regs=IP,SP,BP -- matrix.gcc.g.03
> 
>   188368474305373 0x5e40 [0x470]: PERF_RECORD_SAMPLE(IP, 0x4002): 23839/23839: 0x401236 period: 1260507 addr: 0x7ffd3d85e96c
>   ... FP chain: nr:0
>   ... user regs: mask 0x1c0 ABI 64-bit
>   .... BP    0x401260
>   .... SP    0x7ffd3d85cc20
>   .... IP    0x401236
>   ... ustack: size 1024, offset 0x58
>    . data_src: 0x5080021
>    ... thread: stack_test2.g.O:23839
>    ...... dso: /root/abudanko/stacks/stack_test2.g.O3
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka

> ---
>  tools/perf/util/evsel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 84cfb9fe2fc6..29a223b4c699 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -702,7 +702,8 @@ static void __perf_evsel__config_callchain(struct perf_evsel *evsel,
>  		if (!function) {
>  			perf_evsel__set_sample_bit(evsel, REGS_USER);
>  			perf_evsel__set_sample_bit(evsel, STACK_USER);
> -			attr->sample_regs_user |= PERF_REGS_MASK;
> +			if (!opts->sample_user_regs)
> +				attr->sample_regs_user |= PERF_REGS_MASK;
>  			attr->sample_stack_user = param->dump_size;
>  			attr->exclude_callchain_user = 1;
>  		} else {
> -- 
> 2.20.1
>