linux-kernel - Re: [PATCH 2/9] perf/core: Add PERF_SAMPLE

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Message-ID: <20190831030321.GA93532@google.com>
Date:   Sat, 31 Aug 2019 12:03:26 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature

Hi Tejun,

On Wed, Aug 28, 2019 at 07:49:11AM -0700, Tejun Heo wrote:
> On Wed, Aug 28, 2019 at 04:31:23PM +0900, Namhyung Kim wrote:
> > @@ -958,6 +958,7 @@ struct perf_sample_data {
> >  	u64				stack_user_size;
> >  
> >  	u64				phys_addr;
> > +	u64				cgroup;
> 
> Ditto, please use fhandle as the identifier.

Hmm.. it looks hard to use fhandle as the identifier since perf
sampling is done in NMI context.  AFAICS the encode_fh part seems ok
but getting dentry/inode from a kernfs_node seems not.

I assume kernfs_node_id's ino and gen are same to its inode's.  Then
we might use kernfs_node for encoding but not sure you like it ;-)

Thanks
Namhyung