linux-kernel - Re: [PATCH v1] perf session: fix decompression of PERF_RECORD

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Date:   Mon, 18 Nov 2019 11:46:51 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] perf session: fix decompression of
 PERF_RECORD_COMPRESSED records

On Fri, Nov 15, 2019 at 08:09:19PM +0300, Alexey Budankov wrote:
> 
> On 15.11.2019 18:11, Jiri Olsa wrote:
> > On Fri, Nov 15, 2019 at 12:05:14PM +0300, Alexey Budankov wrote:
> <SNIP>
> >> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> >> index f07b8ecb91bc..3f6f812ec4ed 100644
> >> --- a/tools/perf/util/session.c
> >> +++ b/tools/perf/util/session.c
> >> @@ -1957,9 +1957,31 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
> >>  	return err;
> >>  }
> >>  
> >> +static union perf_event *
> >> +prefetch_event(char *buf, u64 head, size_t mmap_size,
> >> +	       bool needs_swap, union perf_event *ret);
> > 
> > why not move prefetch_event definition in here?
> > I don't see any need for the static declaration..
> 
> It is just for the sake of more readable patch formatting 
> and, yes, could be avoided and replaced by the definition.

I think we're trying to avoid static declarations

> 
> > 
> >> +
> >>  static union perf_event *
> >>  fetch_mmaped_event(struct perf_session *session,
> >>  		   u64 head, size_t mmap_size, char *buf)
> >> +{
> >> +	return prefetch_event(buf, head, mmap_size,
> >> +			      session->header.needs_swap,
> >> +			      ERR_PTR(-EINVAL));
> >> +}
> >> +
> >> +static union perf_event *
> >> +fetch_decomp_event(struct perf_session *session,
> >> +		   u64 head, size_t mmap_size, char *buf)
> >> +{
> > 
> > if this is decomp specific, it could take 'struct decomp*' as argument
> 
> Well, it makes sense. whole session object is not required here.
> Just session->header.needs_swap could be passed as a param.
> Shall we make it like this?
> 
> static union perf_event * 
> fetch_decomp_event(u64 head, size_t mmap_size, char *buf, bool needs_swap)

ok, I just saw the call passing all the stuff from 'struct decomp'
so I thought it'd save some arguments if we pass the  struct itself
instead

jirka