linux-kernel - Re: [RFC][PATCH 0/9] perf trace: support for general-purpose scripting

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:	Tue, 6 Oct 2009 15:53:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Tom Zanussi <tzanussi@...il.com>, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, rostedt@...dmis.org, lizf@...fujitsu.com,
	hch@...radead.org
Subject: Re: [RFC][PATCH 0/9] perf trace: support for general-purpose
	scripting


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, 2009-10-06 at 11:09 +0200, Ingo Molnar wrote:
> > * Tom Zanussi <tzanussi@...il.com> wrote:
> > 
> > > Known problems/shortcomings:
> > > 
> > > Probably the biggest problem right now is the sorting hack I added as 
> > > the last patch.  It's just meant as a temporary thing, but is there 
> > > because tracing scripts in general want to see events in the order 
> > > they happened i.e. timestamp order. [...]
> > 
> > Btw., have you seen the -M/--multiplex option to perf record? It 
> > multiplexes all events into a single buffer - making them all ordered. 
> > (The events are in causal ordering in this case even if there's some TSC 
> > asynchronity)
> 
> It also wrecks large machines.. [...]

With millions of events per sec, for sure. It doesnt with a few thousand 
per sec. Right now that's the price of guarantee causality. If you _can_ 
trust your system-wide TSC then it's not needed - but that's only 
possible on a very small subset of machines currently.

> [...] I've been thinking about limiting the number of CPUs you can 
> redirect into a single output stream using the output_fd thing, but 
> then the inherited stuff makes that very hard.
> 
> And we also need a solution for the inhertited counters, the best 
> would be the per-cpu inherited things, where we use both cpu and pid, 
> instead of either.
> 
> In short, -M is nice, but it also has significant down sides, esp. 
> with machines getting more and more cores.

Yeah.

	Ingo
--
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/