Re: [PATCH v3 7/9] perf config: Add core.hybrid-merge to configure event merging

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] perf: spurious hybrid-merge warning on non-hybrid machines when configured globally
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commit 8278af13a38e06a26581491ef0fd6844e19d37a9
Author: Ian Rogers <irogers@google.com>

perf config: Add core.hybrid-merge to configure event merging

This commit provides a core.hybrid-merge configuration option in
.perfconfig to enable hybrid event aggregation by default. It allows
users to avoid passing the --hybrid-merge flag on every invocation of
perf report or perf top.

> diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
> index b2972c35c1eca..8fe43b032e9af 100644
> --- a/tools/perf/util/config.c
> +++ b/tools/perf/util/config.c
[ ... ]
> @@ -470,6 +470,16 @@ static int perf_default_core_config(const char *var, const char *value)
>  	if (!strcmp(var, "core.addr2line-disable-warn"))
>  		symbol_conf.addr2line_disable_warn = perf_config_bool(var, value);
>  
> +	if (!strcmp(var, "core.hybrid-merge")) {
> +		/*
> +		 * Note, this is for sampling tools like perf report and top.
> +		 * perf stat has its own merging options and the
> +		 * stat_config.hybrid_merge of "perf stat --hybrid-merge" is
> +		 * deliberately not set here.
> +		 */
> +		symbol_conf.hybrid_merge = perf_config_bool(var, value);
> +	}
> +
>  	/* Add other config variables here. */
>  	return 0;
>  }

[Severity: Medium]
When core.hybrid-merge is set globally to true, will this cause spurious
blocking UI warnings on non-hybrid machines?

In both __cmd_report() and __cmd_top(), there is existing code that evaluates
symbol_conf.hybrid_merge. For example, in __cmd_top():

	if (symbol_conf.hybrid_merge) {
		if (evlist__can_merge_hybrid(top->evlist, /*env=*/NULL)) {
			evlist__merge_hybrid(top->evlist, /*env=*/NULL);
			evlist__merge_hists_hybrid(top->evlist, false);
		} else {
			ui__warning("--hybrid-merge: no events to merge across core PMUs\n");
		}
	}

If symbol_conf.hybrid_merge evaluates to true based on the config default,
running perf top or perf report on a non-hybrid system evaluates
evlist__can_merge_hybrid() as false and triggers this warning. 

Because ui__warning() can create a blocking popup in TUI mode requiring user
dismissal, does this break the usability of the tool on generic systems?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260916234652.439778-1-irogers@google.com?part=7