linux-kernel - Re: [PATCH] perf/x86: Fix overlap counter scheduling bug

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Message-ID: <20161108131430.GB4777@krava>
Date:   Tue, 8 Nov 2016 14:14:30 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Vince Weaver <vince@...ter.net>,
        Robert Richter <rric@...nel.org>,
        Yan Zheng <zheng.z.yan@...el.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] perf/x86: Fix overlap counter scheduling bug

On Tue, Nov 08, 2016 at 01:20:39PM +0100, Peter Zijlstra wrote:

SNIP

> Now, I would much rather solve this by changing the constraint like the
> below, that yields:
> 
>  0x01 - 0001
>  0x03 - 0011
> 
>  0x0c - 1100
> 
> Which is two distinct groups, only one of which has overlap. And the one
> with overlap only has 2 overlapping masks, giving a max reties of 1.

works for me.. 

thanks,
jirka

> 
> 
> diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
> index 272427700d48..71bc348736bd 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -669,7 +669,7 @@ static struct event_constraint snbep_uncore_cbox_constraints[] = {
>  	UNCORE_EVENT_CONSTRAINT(0x1c, 0xc),
>  	UNCORE_EVENT_CONSTRAINT(0x1d, 0xc),
>  	UNCORE_EVENT_CONSTRAINT(0x1e, 0xc),
> -	EVENT_CONSTRAINT_OVERLAP(0x1f, 0xe, 0xff),
> +	UNCORE_EVENT_CONSTRAINT(0x1f, 0xc); /* should be 0x0e but that gives scheduling pain */
>  	UNCORE_EVENT_CONSTRAINT(0x21, 0x3),
>  	UNCORE_EVENT_CONSTRAINT(0x23, 0x3),
>  	UNCORE_EVENT_CONSTRAINT(0x31, 0x3),