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Date: Thu, 1 Sep 2022 07:31:58 -0700
From: Andi Kleen <ak@...ux.intel.com>
To: Adrian Hunter <adrian.hunter@...el.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] perf intel-pt: Support itrace option flag d+e to log
on error
On 9/1/2022 4:00 AM, Adrian Hunter wrote:
> Pass d+e option and log size via intel_pt_log_enable(). Allocate a buffer
> for log messages and provide intel_pt_log_dump_buf() to dump and reset the
> buffer upon decoder errors.
>
> Example:
>
> $ sudo perf record -e intel_pt// sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.094 MB perf.data ]
> $ sudo perf config itrace.debug-log-buffer-size=300
> $ sudo perf script --itrace=ed+e+o | head -20
> Dumping debug log buffer (first line may be sliced)
> Other
> ffffffff96ca22f6: 48 89 e5 Other
> ffffffff96ca22f9: 65 48 8b 05 ff e0 38 69 Other
> ffffffff96ca2301: 48 3d c0 a5 c1 98 Other
> ffffffff96ca2307: 74 08 Jcc +8
> ffffffff96ca2311: 5d Other
> ffffffff96ca2312: c3 Ret
> ERROR: Bad RET compression (TNT=N) at 0xffffffff96ca2312
> End of debug log buffer dump
> instruction trace error type 1 time 15913.537143482 cpu 5 pid 36292 tid 36292 ip 0xffffffff96ca2312 code 6: Trace doesn't match instruction
> Dumping debug log buffer (first line may be sliced)
> Other
> ffffffff96ce7fe9: f6 47 2e 20 Other
> ffffffff96ce7fed: 74 11 Jcc +17
> ffffffff96ce7fef: 48 8b 87 28 0a 00 00 Other
> ffffffff96ce7ff6: 5d Other
> ffffffff96ce7ff7: 48 8b 40 18 Other
> ffffffff96ce7ffb: c3 Ret
> ERROR: Bad RET compression (TNT=N) at 0xffffffff96ce7ffb
> Warning:
> 8 instruction trace errors
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
> tools/perf/Documentation/perf-intel-pt.txt | 5 +-
> .../perf/util/intel-pt-decoder/intel-pt-log.c | 94 ++++++++++++++++++-
> .../perf/util/intel-pt-decoder/intel-pt-log.h | 3 +-
> tools/perf/util/intel-pt.c | 20 +++-
> 4 files changed, 117 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
> index d5ddb968bcf4..92464a5d7eaf 100644
> --- a/tools/perf/Documentation/perf-intel-pt.txt
> +++ b/tools/perf/Documentation/perf-intel-pt.txt
> @@ -989,10 +989,13 @@ must be preceded by either '+' or '-'. The flags support by Intel PT are:
>
> -a Suppress logging of perf events
> +a Log all perf events
> + +e Output only on decoding errors (size configurable)
> +o Output to stdout instead of "intel_pt.log"
>
> By default, logged perf events are filtered by any specified time ranges, but
> -flag +a overrides that.
> +flag +a overrides that. The +e flag can be useful for analyzing errors. By
> +default, the log size in that case is 16384 bytes, but can be altered by
> +linkperf:perf-config[1] e.g. perf config itrace.debug-log-buffer-size=30000
>
> In addition, the period of the "instructions" event can be specified. e.g.
>
> diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-log.c b/tools/perf/util/intel-pt-decoder/intel-pt-log.c
> index 5f5dfc8753f3..ea96dcae187a 100644
> --- a/tools/perf/util/intel-pt-decoder/intel-pt-log.c
> +++ b/tools/perf/util/intel-pt-decoder/intel-pt-log.c
> @@ -5,12 +5,16 @@
> */
>
> #include <stdio.h>
> +#include <stdlib.h>
> #include <stdint.h>
> #include <inttypes.h>
> #include <stdarg.h>
> #include <stdbool.h>
> #include <string.h>
>
> +#include <linux/zalloc.h>
> +#include <linux/kernel.h>
> +
> #include "intel-pt-log.h"
> #include "intel-pt-insn-decoder.h"
>
> @@ -21,15 +25,20 @@
> static FILE *f;
> static char log_name[MAX_LOG_NAME];
> bool intel_pt_enable_logging;
> +static bool intel_pt_dump_log_on_error;
> +static unsigned int intel_pt_log_on_error_size;
> +static struct log_buf log_buf;
>
> void *intel_pt_log_fp(void)
> {
> return f;
> }
>
> -void intel_pt_log_enable(void)
> +void intel_pt_log_enable(bool dump_log_on_error, unsigned int log_on_error_size)
> {
> intel_pt_enable_logging = true;
> + intel_pt_dump_log_on_error = dump_log_on_error;
> + intel_pt_log_on_error_size = log_on_error_size;
> }
>
> void intel_pt_log_disable(void)
> @@ -74,6 +83,87 @@ static void intel_pt_print_no_data(uint64_t pos, int indent)
> fprintf(f, " ");
> }
>
> +#define DFLT_BUF_SZ (16 * 1024)
> +
> +struct log_buf {
> + char *buf;
> + size_t buf_sz;
> + size_t head;
> + bool wrapped;
> + FILE *backend;
> +};
> +
> +static ssize_t log_buf__write(void *cookie, const char *buf, size_t size)
> +{
> + struct log_buf *b = cookie;
> + size_t sz = size;
> +
> + if (!b->buf)
> + return size;
> +
> + while (sz) {
> + size_t space = b->buf_sz - b->head;
> + size_t n = min(space, sz);
> +
> + memcpy(b->buf + b->head, buf, n);
> + sz -= n;
> + buf += n;
> + b->head += n;
> + if (sz && b->head >= b->buf_sz) {
> + b->head = 0;
> + b->wrapped = true;
> + }
> + }
I would add an assert or somesuch for the case where sz is larger than
the buffer size, which would otherwise loop forever.
> +
> +static void log_buf__dump(struct log_buf *b)
> +{
> + if (!b->buf)
> + return;
> +
> + fflush(f);
> + fprintf(b->backend, "Dumping debug log buffer (first line may be sliced)\n");
Should be easy to skip the first line, no?
Rest looks good.
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
-Andi
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