From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753205AbdESMLH (ORCPT <rfc822;w@1wt.eu>);
        Fri, 19 May 2017 08:11:07 -0400
Received: from bombadil.infradead.org ([65.50.211.133]:57097 "EHLO
        bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750728AbdESMLF (ORCPT
        <rfc822;Linux-kernel@vger.kernel.org>);
        Fri, 19 May 2017 08:11:05 -0400
Date: Fri, 19 May 2017 14:10:56 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: "Jin, Yao" <yao.jin@linux.intel.com>
Cc: acme@kernel.org, jolsa@kernel.org, mingo@redhat.com,
        alexander.shishkin@linux.intel.com, Linux-kernel@vger.kernel.org,
        ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com,
        Will Deacon <will.deacon@arm.com>, Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is
 specified
Message-ID: <20170519121056.c45jbsfgcdjfuoow@hirez.programming.kicks-ass.net>
References: <1495189152-5766-1-git-send-email-yao.jin@linux.intel.com>
 <20170519092905.yivnfjyhblm5wiap@hirez.programming.kicks-ass.net>
 <eba28230-5a96-fbfe-0fb3-191921839a72@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <eba28230-5a96-fbfe-0fb3-191921839a72@linux.intel.com>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, May 19, 2017 at 08:06:09PM +0800, Jin, Yao wrote:
> SNIP
> 
> > I would much rather see this in generic code, somewhere around
> > __perf_event_overflow() I suppose. That would retain proper accounting
> > for the interrupt rate etc..
> > 
> > Also it would work for all architectures. Because I'm thinking more than
> > just x86 will suffer from skid.
> Yes, moving to generic code is better.  Thanks for the suggestion! I will do
> that.
> 
> > If you're really worried, I suppose you can put it behind a PERF_PMU_CAP
> > flag or something.
> I guess what you are suggesting is to add checking like:
> 
> if (is_sampling_event(event)) {
>     if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
>         return;
>     }
> }

Ah, I was more thinking of something like PERF_PMU_CAP_NO_SKID or
something that would skip the test and preserve current behaviour.