Subject: Re: [PATCH v6 1/3] perf/core: use rb trees for pinned/flexible groups
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Kan Liang <kan.liang@intel.com>,
        Dmitri Prokhorov <Dmitry.Prohorov@intel.com>,
        Valery Cherepennikov <valery.cherepennikov@intel.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Stephane Eranian <eranian@google.com>,
        David Carrillo-Cisneros <davidcc@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
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From: Alexey Budankov <alexey.budankov@linux.intel.com>
Organization: Intel Corp.
Message-ID: <15ee5ae7-cdd0-d93f-0e66-a83f16eb9e6b@linux.intel.com>
Date: Mon, 7 Aug 2017 21:13:47 +0300
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On 07.08.2017 19:57, Peter Zijlstra wrote:
> On Mon, Aug 07, 2017 at 07:27:30PM +0300, Alexey Budankov wrote:
>> On 07.08.2017 18:55, Peter Zijlstra wrote:
> 
>>> In the extreme, if you construct your program such that you'll never get
>>> hit by the tick (this used to be a popular measure to hide yourself from
>>> time accounting)
>>
>> Well, some weird thing for me. Never run longer than one tick? 
>> I could imaging some I/O bound code that would fast serve some short 
>> messages, all the other time waiting for incoming requests.
>> Not sure if CPU events monitoring is helpful in this case.
> 
> Like I said, in extreme. Typically its less weird.> 
> Another example is scheduling a very constrained counter/group along
> with a bunch of simple events such that the group will only succeed to
> schedule when its the first. In this case it will get only 1/nr_events
> time with RR, as opposed to the other/simple events that will get
> nr_counters/nr_events time.
> 
> By making it runtime based, the constrained thing will more often be
> head of list and acquire equal total runtime to the other events.

I see and what could be the triggering condition for runtime based scheduling 
of groups as an alternative to hrtimer signal?

>