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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 13 Dec 2010 18:09:26 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	"David S. Ahern" <daahern@...co.com>,
	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 02:48:54PM -0200, Arnaldo Carvalho de Melo wrote:
> Em Mon, Dec 13, 2010 at 04:54:56PM +0100, Frederic Weisbecker escreveu:
> > 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.
> 
> Right, but it just ocurred to me, can't we encode this in the file stat?
> Also, how do we deal with:
> 
> $ perf record --help
> <SNIP>
>        -A, --append
>            Append to the output file to do incremental profiling.
> <SNIP>
> 
> ?
> 
> I now think this should be implemented as a PERF_RECORD_WALL_CLOCK
> synthesized event, to be inserted just before we start collecting the
> other events.
> 
> That way, when --appending, we just insert another and use that from
> that point on.
> 
> Look at tools/perf/util/event.h, enum perf_user_event_type and look how
> those are synthesized.
> 
> Thanks,
> 
> - Arnaldo

(Adding peterz)

Right, but Peter wanted us to get rid of these user events types.
I guess we can't really do this as new perf tools must be able
to support old perf files.

So this should be the last one to add. Something like PERF_RECORD_GEN_EVT
that has a field in its headers containing a sub-type which can be this
wall clock but can also host about everything in the future.

This way we don't propagate more the possible overlap with the kernel.

Hm?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/