Re: [PATCH v3] perf annotate: Cache debuginfo for data type profiling

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Aug 05, 2024 at 04:46:48PM -0700, Namhyung Kim wrote:
> In find_data_type(), it creates and deletes a debug info whenver it
> tries to find data type for a sample.  This is inefficient and it most
> likely accesses the same binary again and again.
> 
> Let's add a single entry cache the debug info structure for the last DSO.
> Depending on sample data, it usually gives me 2~3x (and sometimes more)
> speed ups.
> 
> Note that this will introduce a little difference in the output due to
> the order of checking stack operations.  It used to check the stack ops
> before checking the availability of debug info but I moved it after the
> symbol check.  So it'll report stack operations in DSOs without debug
> info as unknown.  But I think it's ok and better to have the checking
> near the caching logic.

Thanks, tested and applied.

- Arnaldo
 
> Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
> v2) add an assertion for the single-threaded case.
> v3) update the comment according to Ian.
> 
>  tools/perf/util/annotate-data.c | 15 ++-----------
>  tools/perf/util/annotate-data.h |  2 +-
>  tools/perf/util/annotate.c      | 37 +++++++++++++++++++++++++++++++++
>  tools/perf/util/annotate.h      |  2 ++
>  tools/perf/util/session.c       |  2 ++
>  5 files changed, 44 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
> index 734acdd8c4b7..f125ac5f0bda 100644
> --- a/tools/perf/util/annotate-data.c
> +++ b/tools/perf/util/annotate-data.c
> @@ -1345,16 +1345,9 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die)
>   */
>  struct annotated_data_type *find_data_type(struct data_loc_info *dloc)
>  {
> -	struct annotated_data_type *result = NULL;
>  	struct dso *dso = map__dso(dloc->ms->map);
>  	Dwarf_Die type_die;
>  
> -	dloc->di = debuginfo__new(dso__long_name(dso));
> -	if (dloc->di == NULL) {
> -		pr_debug_dtp("cannot get the debug info\n");
> -		return NULL;
> -	}
> -
>  	/*
>  	 * The type offset is the same as instruction offset by default.
>  	 * But when finding a global variable, the offset won't be valid.
> @@ -1364,13 +1357,9 @@ struct annotated_data_type *find_data_type(struct data_loc_info *dloc)
>  	dloc->fbreg = -1;
>  
>  	if (find_data_type_die(dloc, &type_die) < 0)
> -		goto out;
> -
> -	result = dso__findnew_data_type(dso, &type_die);
> +		return NULL;
>  
> -out:
> -	debuginfo__delete(dloc->di);
> -	return result;
> +	return dso__findnew_data_type(dso, &type_die);
>  }
>  
>  static int alloc_data_type_histograms(struct annotated_data_type *adt, int nr_entries)
> diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h
> index 992b7ce4bd11..37a1a3b68e0b 100644
> --- a/tools/perf/util/annotate-data.h
> +++ b/tools/perf/util/annotate-data.h
> @@ -123,9 +123,9 @@ struct data_loc_info {
>  	u64 var_addr;
>  	u8 cpumode;
>  	struct annotated_op_loc *op;
> +	struct debuginfo *di;
>  
>  	/* These are used internally */
> -	struct debuginfo *di;
>  	int fbreg;
>  	bool fb_cfa;
>  
> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> index a2ee4074f768..a28d8a4b8a14 100644
> --- a/tools/perf/util/annotate.c
> +++ b/tools/perf/util/annotate.c
> @@ -25,6 +25,7 @@
>  #include "srcline.h"
>  #include "units.h"
>  #include "debug.h"
> +#include "debuginfo.h"
>  #include "annotate.h"
>  #include "annotate-data.h"
>  #include "evsel.h"
> @@ -2326,6 +2327,20 @@ u64 annotate_calc_pcrel(struct map_symbol *ms, u64 ip, int offset,
>  	return map__rip_2objdump(ms->map, addr);
>  }
>  
> +static struct debuginfo_cache {
> +	struct dso *dso;
> +	struct debuginfo *dbg;
> +} di_cache;
> +
> +void debuginfo_cache__delete(void)
> +{
> +	dso__put(di_cache.dso);
> +	di_cache.dso = NULL;
> +
> +	debuginfo__delete(di_cache.dbg);
> +	di_cache.dbg = NULL;
> +}
> +
>  /**
>   * hist_entry__get_data_type - find data type for given hist entry
>   * @he: hist entry
> @@ -2360,6 +2375,27 @@ struct annotated_data_type *hist_entry__get_data_type(struct hist_entry *he)
>  		return NULL;
>  	}
>  
> +	/*
> +	 * di_cache holds a pair of values, but code below assumes
> +	 * di_cache.dso can be compared/updated and di_cache.dbg can be
> +	 * read/updated independently from each other. That assumption only
> +	 * holds in single threaded code.
> +	 */
> +	assert(perf_singlethreaded);
> +
> +	if (map__dso(ms->map) != di_cache.dso) {
> +		dso__put(di_cache.dso);
> +		di_cache.dso = dso__get(map__dso(ms->map));
> +
> +		debuginfo__delete(di_cache.dbg);
> +		di_cache.dbg = debuginfo__new(dso__long_name(di_cache.dso));
> +	}
> +
> +	if (di_cache.dbg == NULL) {
> +		ann_data_stat.no_dbginfo++;
> +		return NULL;
> +	}
> +
>  	/* Make sure it has the disasm of the function */
>  	if (symbol__annotate(ms, evsel, &arch) < 0) {
>  		ann_data_stat.no_insn++;
> @@ -2404,6 +2440,7 @@ struct annotated_data_type *hist_entry__get_data_type(struct hist_entry *he)
>  			.ip = ms->sym->start + dl->al.offset,
>  			.cpumode = he->cpumode,
>  			.op = op_loc,
> +			.di = di_cache.dbg,
>  		};
>  
>  		if (!op_loc->mem_ref && op_loc->segment == INSN_SEG_NONE)
> diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
> index 9ba772f46270..27d9540604ef 100644
> --- a/tools/perf/util/annotate.h
> +++ b/tools/perf/util/annotate.h
> @@ -543,4 +543,6 @@ struct annotated_basic_block {
>  int annotate_get_basic_blocks(struct symbol *sym, s64 src, s64 dst,
>  			      struct list_head *head);
>  
> +void debuginfo_cache__delete(void);
> +
>  #endif	/* __PERF_ANNOTATE_H */
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 5596bed1b8c8..f9072e003367 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -36,6 +36,7 @@
>  #include "util.h"
>  #include "arch/common.h"
>  #include "units.h"
> +#include "annotate.h"
>  #include <internal/lib.h>
>  
>  #ifdef HAVE_ZSTD_SUPPORT
> @@ -304,6 +305,7 @@ void perf_session__delete(struct perf_session *session)
>  		return;
>  	auxtrace__free(session);
>  	auxtrace_index__free(&session->auxtrace_index);
> +	debuginfo_cache__delete();
>  	perf_session__destroy_kernel_maps(session);
>  	perf_decomp__release_events(session->decomp_data.decomp);
>  	perf_env__exit(&session->header.env);
> -- 
> 2.46.0.rc2.264.g509ed76dc8-goog