Re: [PATCH v4 12/15] perf report: cache failed lookups of inlined frames

Namhyung Kim
2017-10-05T03:46:07Z

On Sun, Oct 01, 2017 at 04:30:57PM +0200, Milian Wolff wrote:
> When no inlined frames could be found for a given address,
> we did not store this information anywhere. That means we
> potentially do the costly inliner lookup repeatedly for
> cases where we know it can never succeed.
>
> This patch makes dso__parse_addr_inlines always return a
> valid inline_node. It will be empty when no inliners are
> found. This enables us to cache the empty list in the DSO,
> thereby improving the performance when many addresses
> fail to find the inliners.
>
> For my trivial example, the performance impact is already
> quite significant:
>
> Before:
>
> ~~~~~
> Performance counter stats for 'perf report --stdio --inline -g srcline -s srcline' (5 runs):
>
> 594.804032 task-clock (msec) # 0.998 CPUs utilized ( +- 0.07% )
> 53 context-switches # 0.089 K/sec ( +- 4.09% )
> 0 cpu-migrations # 0.000 K/sec ( +-100.00% )
> 5,687 page-faults # 0.010 M/sec ( +- 0.02% )
> 2,300,918,213 cycles # 3.868 GHz ( +- 0.09% )
> 4,395,839,080 instructions # 1.91 insn per cycle ( +- 0.00% )
> 939,177,205 branches # 1578.969 M/sec ( +- 0.00% )
> 11,824,633 branch-misses # 1.26% of all branches ( +- 0.10% )
>
> 0.596246531 seconds time elapsed ( +- 0.07% )
> ~~~~~
>
> After:
>
> ~~~~~
> Performance counter stats for 'perf report --stdio --inline -g srcline -s srcline' (5 runs):
>
> 113.111405 task-clock (msec) # 0.990 CPUs utilized ( +- 0.89% )
> 29 context-switches # 0.255 K/sec ( +- 54.25% )
> 0 cpu-migrations # 0.000 K/sec
> 5,380 page-faults # 0.048 M/sec ( +- 0.01% )
> 432,378,779 cycles # 3.823 GHz ( +- 0.75% )
> 670,057,633 instructions # 1.55 insn per cycle ( +- 0.01% )
> 141,001,247 branches # 1246.570 M/sec ( +- 0.01% )
> 2,346,845 branch-misses # 1.66% of all branches ( +- 0.19% )
>
> 0.114222393 seconds time elapsed ( +- 1.19% )
> ~~~~~
>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Yao Jin <yao.jin@linux.intel.com>
> Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
> ---

[SNIP]

> diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
> index 69241d805275..26d9954dc19e 100644
> --- a/tools/perf/util/srcline.c
> +++ b/tools/perf/util/srcline.c
> @@ -353,17 +353,8 @@ static struct inline_node *addr2inlines(const char *dso_name, u64 addr,
> INIT_LIST_HEAD(&node->val);
> node->addr = addr;
>
> - if (!addr2line(dso_name, addr, NULL, NULL, dso, TRUE, node, sym))
> - goto out_free_inline_node;
> -
> - if (list_empty(&node->val))
> - goto out_free_inline_node;
> -
> - return node;
> -
> -out_free_inline_node:
> - inline_node__delete(node);
> - return NULL;
> + addr2line(dso_name, addr, NULL, NULL, dso, TRUE, node, sym);
> + return node;

Whitespace demanged.

Also please use 'true' instead of 'TRUE' for consistency (I know this
is not your fault).

Thanks,
Namhyung

> }
>
> #else /* HAVE_LIBBFD_SUPPORT */
> @@ -480,11 +471,6 @@ static struct inline_node *addr2inlines(const char *dso_name, u64 addr,
> out:
> pclose(fp);
>
> - if (list_empty(&node->val)) {
> - inline_node__delete(node);
> - return NULL;
> - }
> -
> return node;
> }
>
> --
> 2.14.2
>