linux-kernel - Re: [PATCH v2 11/27] perf parse-events: Support hardware events inside PMU

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Date:   Mon, 15 Mar 2021 18:37:46 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Jin, Yao" <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v2 11/27] perf parse-events: Support hardware events
 inside PMU

On Mon, Mar 15, 2021 at 10:28:12AM +0800, Jin, Yao wrote:
> Hi Jiri,
> 
> On 3/13/2021 3:15 AM, Jiri Olsa wrote:
> > On Thu, Mar 11, 2021 at 03:07:26PM +0800, Jin Yao wrote:
> > > On hybrid platform, some hardware events are only available
> > > on a specific pmu. For example, 'L1-dcache-load-misses' is only
> > > available on 'cpu_core' pmu. And even for the event which can be
> > > available on both pmus, the user also may want to just enable
> > > one event. So now following syntax is supported:
> > > 
> > > cpu_core/<hardware event>/
> > > cpu_core/<hardware cache event>/
> > > cpu_core/<pmu event>/
> > > 
> > > cpu_atom/<hardware event>/
> > > cpu_atom/<hardware cache event>/
> > > cpu_atom/<pmu event>/
> > > 
> > > It limits the event to be enabled only on a specified pmu.
> > > 
> > > The patch uses this idea, for example, if we use "cpu_core/LLC-loads/",
> > > in parse_events_add_pmu(), term->config is "LLC-loads".
> > 
> > hum, I don't understand how this doest not work even now,
> > I assume both cpu_core and cpu_atom have sysfs device directory
> > with events/ directory right?
> > 
> 
> Yes, we have cpu_core and cpu_atom directories with events.
> 
> root@...-pwrt-002:/sys/devices/cpu_atom/events# ls
> branch-instructions  bus-cycles    cache-references  instructions
> mem-stores  topdown-bad-spec topdown-fe-bound
> branch-misses        cache-misses  cpu-cycles        mem-loads
> ref-cycles  topdown-be-bound topdown-retiring
> 
> root@...-pwrt-002:/sys/devices/cpu_core/events# ls
> branch-instructions  cache-misses      instructions   mem-stores
> topdown-bad-spec topdown-fe-bound   topdown-mem-bound
> branch-misses        cache-references  mem-loads      ref-cycles
> topdown-be-bound topdown-fetch-lat  topdown-retiring
> bus-cycles           cpu-cycles        mem-loads-aux  slots
> topdown-br-mispredict topdown-heavy-ops
> 
> > and whatever is defined in events we allow in parsing syntax..
> > 
> > why can't we treat them like 2 separated pmus?
> > 
> 
> But if without this patch, it reports the error,
> 
> root@...-pwrt-002:~# ./perf stat -e cpu_core/cycles/ -a -vv -- sleep 1
> event syntax error: 'cpu_core/cycles/'
>                               \___ unknown term 'cycles' for pmu 'cpu_core'

yep, because there's special care for 'cycles' unfortunately,
but you should be able to run 'cpu_core/cpu-cycles/' right?

> 
> valid terms: event,pc,edge,offcore_rsp,ldlat,inv,umask,frontend,cmask,config,config1,config2,name,period,percore
> 
> Initial error:
> event syntax error: 'cpu_core/cycles/'
>                               \___ unknown term 'cycles' for pmu 'cpu_core'
> 
> valid terms: event,pc,edge,offcore_rsp,ldlat,inv,umask,frontend,cmask,config,config1,config2,name,period,percore
> Run 'perf list' for a list of valid events
> 
> The 'cycles' is treated as a unknown term, then it errors out.

yep, because it's not in events.. we could add special rule to
treat cycles as cpu-cycles inside pmu definition ;-)

jirka