linux-kernel - Re: [PATCH 6/6] x86: Allow disabling HW_BREAKPOINTS and PERF

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Date:	Tue, 8 Oct 2013 21:36:13 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dave Jones <davej@...hat.com>, David Ahern <dsahern@...il.com>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	Andi Kleen <ak@...ux.intel.com>, fweisbec@...il.com
Subject: Re: [PATCH 6/6] x86: Allow disabling HW_BREAKPOINTS and PERF_EVENTS


* Dave Jones <davej@...hat.com> wrote:

> On Tue, Oct 08, 2013 at 10:22:23AM -0600, David Ahern wrote:
>  > On 10/8/13 9:51 AM, Dave Jones wrote:
>  > > On Tue, Oct 08, 2013 at 08:59:38AM +0200, Ingo Molnar wrote:
>  > >
>  > >   > You might want to concentrate your efforts from fighting perf
>  > >   > functionality towards decreasing per tracepoint overhead instead,
>  > >   > without hurting kernel functionality and maintainability.
>  > >
>  > > Making it easier to disable perf entirely would be desirable for one use case.
>  > > I can't do a trinity run for more than a few hours for the last few months
>  > > without hitting perf/ftrace bugs that no-one seems to be able to get their
>  > > heads around.
>  > 
>  > Looks like trinity has an exclude syscall option. Seems like that option 
>  > can be used to avoid perf_event_open (haven't tried though).
> 
> You'd think that, but for whatever reason, ftrace/perf oopses still happen.

Peter is working on it - but it's slow. Could you try to disable 
sys_perf_open, ptrace and the NMI watchdog? No perf functionality should 
be used in that case. If you disable CONFIG_FTRACE then no ftrace 
functionality should be used.

Thanks,
	
	Ingo
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