linux-kernel - Re: perf_event: rdpmc self-monitoring overhead issue

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20130902172659.GJ19750@two.firstfloor.org>
Date:	Mon, 2 Sep 2013 19:26:59 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	eranian@...il.com, Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: perf_event: rdpmc self-monitoring overhead issue

> I assume he means MAP_POPULATE

Yes.

> 
> which does improve things, from ~3000 cycles to ~219 cycles but that's 
> still more overhead than the ~130 or so you get by manually touching the 
> page first.

That seems odd. It should be the same.

Can you do a trace-cmd function trace and compare the two cases?

trace-cmd record -p function_graph ...
trace-cmd report

(as usual for tracing perf remove the useless -pg removal for perf in
kernel/events/Makefile and arch/x86/kernel/cpu/Makefile first)

-Andi
--
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/