linux-kernel - Re: [PATCH 1/2] perf tools: Add reference timestamp to perf header

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Message-ID: <20101213155451.GA1691@nowhere>
Date:	Mon, 13 Dec 2010 16:54:56 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	"David S. Ahern" <daahern@...co.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] perf tools: Add reference timestamp to perf header

On Mon, Dec 13, 2010 at 07:39:24AM -0700, David S. Ahern wrote:
> 
> 
> On 12/12/10 13:16, Frederic Weisbecker wrote:
> 
> >>  int perf_session__create_kernel_maps(struct perf_session *self)
> >>  {
> >>  	int ret = machine__create_kernel_maps(&self->host_machine);
> >> @@ -167,6 +190,9 @@ struct perf_session *perf_session__new(const char *filename, int mode, bool forc
> >>  		 */
> >>  		if (perf_session__create_kernel_maps(self) < 0)
> >>  			goto out_delete;
> >> +
> >> +		if (perf_session__create_ref_time(self) < 0)
> >> +			goto out_delete;
> > 
> > So, it does record it anytime?
> 
> Simplest to always add it the header as it does no harm if not used. To
> make it conditional means adding an input parameter to
> perf_session__new() and then updating all the callers.
> 
> Is the preference to make it conditional?

No, I suspect the overhead is plain unnoticeable. And if it becomes
any problem one day, we can still make that conditional later.

Thanks.
 
> David
> 
> 
> > 
> >>  	}
> >>  
> >>  	perf_session__update_sample_type(self);
> > 
> > 
> > Other than that, looks good!
> > --
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