linux-kernel - Re: [PATCH 2/3] perf alias: Rebuild alias expression string to make it comparable

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Message-ID: <20180615092700.GH5082@krava>
Date:   Fri, 15 Jun 2018 11:27:00 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Thomas-Mich Richter <tmricht@...ux.ibm.com>
Cc:     Paul Clarke <pc@...ibm.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, acme@...nel.org,
        brueckner@...ux.vnet.ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com
Subject: Re: [PATCH 2/3] perf alias: Rebuild alias expression string to make
 it comparable

On Fri, Jun 15, 2018 at 11:09:05AM +0200, Thomas-Mich Richter wrote:
> On 06/15/2018 10:12 AM, Jiri Olsa wrote:
> > On Thu, Jun 14, 2018 at 08:53:14AM -0500, Paul Clarke wrote:
> > 
> > SNIP
> > 
> >>> +		if (ret)
> >>> +			ret += scnprintf(newval + ret, sizeof(newval) - ret,
> >>> +					 ",");
> >>> +		if (term->type_val == PARSE_EVENTS__TERM_TYPE_NUM)
> >>> +			ret += scnprintf(newval + ret, sizeof(newval) - ret,
> >>> +					 "%s=%#x", term->config, term->val.num);
> >>> +		else if (term->type_val == PARSE_EVENTS__TERM_TYPE_STR)
> >>> +			ret += scnprintf(newval + ret, sizeof(newval) - ret,
> >>> +					 "%s=%s", term->config, term->val.str);
> >>
> >> If we exceed 256, we just suddenly terminate the rebuilding without reporting any issues.
> >>
> >>> +	}
> >>> +
> >>>  	alias->name = strdup(name);
> >>>  	if (dir) {
> >>>  		/*
> >>> @@ -285,7 +308,7 @@ static int __perf_pmu__new_alias(struct list_head *list, char *dir, char *name,
> >>>  		snprintf(alias->unit, sizeof(alias->unit), "%s", unit);
> >>>  	}
> >>>  	alias->per_pkg = perpkg && sscanf(perpkg, "%d", &num) == 1 && num == 1;
> >>> -	alias->str = strdup(val);
> >>> +	alias->str = strdup(newval);
> > 
> > hum, how is newval different from val? AFAICS it's the same
> > 
> 
> Not really, depends on the platform, here is some debug output from s390:
> root@...lp76 perf]# ./perf stat -e tx_nc_tend -- ~/mytesttx 1 >/tmp/111
> 
>  Performance counter stats for '/root/mytesttx 1':
> 
>                  1      tx_nc_tend                                                  
> 
>        0.001050150 seconds time elapsed
> 
> [root@...lp76 perf]# fgrep -i tx_nc_tend /tmp/111
> __perf_pmu__new_alias TX_NC_TEND val:event=0x008d newval:event=0x8d
> __perf_pmu__new_alias tx_nc_tend val:event=0x8d newval:event=0x8d
> TX_NC_TEND	1 rc 8
> [root@...lp76 perf]# 
> 
> On s390 the events in the PMU sysfs file are printed with leading zeroes.
> This means the strcmp() of alias->str differs, but the contents is logically
> identical. (Same of some files contains spaces).
> 
> Thats why I do the rewrite of val into newval.
> 
> The alias name does not match too, but we use strcasecmp() to ignore case.
> 
> Hope this helps.

yep.. should have read the full change log ;-) thanks

jirka