Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 16 Oct 2018 20:10:15 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Song Liu <songliubraving@fb.com>
Cc:     Ingo Molnar <mingo@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        "acme@kernel.org" <acme@kernel.org>,
        "alexander.shishkin@linux.intel.com" 
        <alexander.shishkin@linux.intel.com>,
        "jolsa@redhat.com" <jolsa@redhat.com>,
        "eranian@google.com" <eranian@google.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "alexey.budankov@linux.intel.com" <alexey.budankov@linux.intel.com>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "megha.dey@intel.com" <megha.dey@intel.com>,
        "frederic@kernel.org" <frederic@kernel.org>
Subject: Re: [RFC][PATCH] perf: Rewrite core context handling
Message-ID: <20181016181015.GD3121@hirez.programming.kicks-ass.net>
References: <20181010104559.GO5728@hirez.programming.kicks-ass.net>
 <D2014055-9B25-4152-A582-7AD42A3837AB@fb.com>
 <20181011092913.GA9848@hirez.programming.kicks-ass.net>
 <70079805-1CAE-4CAA-813A-F8DDB929F22B@fb.com>
 <20181012095001.GG9867@hirez.programming.kicks-ass.net>
 <E4F81A5E-C371-429D-AFEC-6F4B32971F09@fb.com>
 <20181016095056.GE4030@hirez.programming.kicks-ass.net>
 <9865C981-0E8C-4419-AE8C-638DCD40D74E@fb.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <9865C981-0E8C-4419-AE8C-638DCD40D74E@fb.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Oct 16, 2018 at 04:34:05PM +0000, Song Liu wrote:
> >> 3. perf_event_pmu_context owns RB tree of events. Since we don't 
> >>   need rotation across multiple hardware PMUs, the rotation is 
> >>   within same perf_event_pmu_context.  
> > 
> > By keeping the RB trees in perf_event_context, we get bigger trees,
> > which is more efficient (log(n+m) < log(n) + log(m))
> > 
> > Also, specifically, it means we only need a single merge sort /
> > iteration to schedule in a full context, instead of (again) doing 'n' of
> > them.
> > 
> > Also, given a context and a pmu, it is cheaper for finding the relevant
> > events; this is needed for big.little for instance. Something the
> > proposed patch doesn't fully flesh out.
> 
> Would it be faster if we add a perf_event_pmu_context pointer to the 
> perf_event? 

+       pmu_ctx = find_get_pmu_context(pmu, ctx, event);
+       if (IS_ERR(pmu_ctx)) {
+               err = PTR_ERR(pmu_ctx);
+               goto err_locked;
+       }
+       event->pmu_ctx = pmu_ctx;

Like that?