From: Peter Zijlstra <peterz@infradead.org>
To: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
arnd@arndb.de, Alexey Brodkin <Alexey.Brodkin@synopsys.com>,
arc-linux-dev@synopsys.com,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH 4/8] ARCv2: perf: Support sampling events using overflow interrupts
Date: Mon, 15 Jun 2015 17:48:16 +0200 [thread overview]
Message-ID: <20150615154816.GG3644@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1433852372-29494-5-git-send-email-vgupta@synopsys.com>
On Tue, Jun 09, 2015 at 05:49:28PM +0530, Vineet Gupta wrote:
> From: Alexey Brodkin <abrodkin@synopsys.com>
-ENOCHANGELOG
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> ---
> struct arc_pmu {
> struct pmu pmu;
> + int has_interrupts;
we have pmu::flags & PERF_PMU_CAP_NO_INTERRUPT
> @@ -186,7 +189,8 @@ static int arc_pmu_event_init(struct perf_event *event)
> hwc->last_period = hwc->sample_period;
> local64_set(&hwc->period_left, hwc->sample_period);
> } else
> - return -ENOENT;
> + if (!arc_pmu->has_interrupts)
> + return -ENOENT;
Same as before, first determine if the event is yours, then return a
fatal error.
> @@ -307,6 +311,17 @@ static void arc_pmu_stop(struct perf_event *event, int flags)
> struct hw_perf_event *hwc = &event->hw;
> int idx = hwc->idx;
>
> + /* Disable interrupt for this counter */
> + if (is_sampling_event(event)) {
but but but, a sampling event needs the interrupt enabled?
> + /*
> + * Reset interrupt flag by writing of 1. This is required
> + * to make sure pending interrupt was not left.
> + */
Would not typically the interrupt latch be a property of the interrupt
controller, not the device generating it?
That is, how can the device programming affect pending interrupts?
> + write_aux_reg(ARC_REG_PCT_INT_ACT, 1 << idx);
> + write_aux_reg(ARC_REG_PCT_INT_CTRL,
> + read_aux_reg(ARC_REG_PCT_INT_CTRL) & ~(1 << idx));
> + }
> +
> + if (is_sampling_event(event)) {
> + /* Mimic full counter overflow as other arches do */
With this you mean the pretending we have 63bit of overflow counter?
> + write_aux_reg(ARC_REG_PCT_INT_CNTL, arc_pmu->max_period &
> + 0xffffffff);
Would not (u32)arc_pmu->max_period, be clearer?
> + write_aux_reg(ARC_REG_PCT_INT_CNTH,
> + (arc_pmu->max_period >> 32));
But should you not program: min(period, max_period) instead? If the
requested period is shorter than your max period you do not want to
program the max. Or are you missing a negative somewhere?
That is, program the max_period for !sampling events to deal with
overflow folding.
> +
> + /* Enable interrupt for this counter */
> + write_aux_reg(ARC_REG_PCT_INT_CTRL,
> + read_aux_reg(ARC_REG_PCT_INT_CTRL) | (1 << idx));
> + }
> +
> write_aux_reg(ARC_REG_PCT_CONFIG, 0);
> write_aux_reg(ARC_REG_PCT_COUNTL, 0);
> write_aux_reg(ARC_REG_PCT_COUNTH, 0);
next prev parent reply other threads:[~2015-06-15 15:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-09 12:19 [PATCH 0/8] ARCv2 port to Linux - (C) perf Vineet Gupta
2015-06-09 12:19 ` [PATCH 1/8] ARC: perf: support RAW events Vineet Gupta
2015-06-15 15:30 ` Peter Zijlstra
2015-06-16 11:45 ` Alexey Brodkin
2015-06-17 13:33 ` Peter Zijlstra
2015-06-17 14:10 ` Vineet Gupta
2015-06-22 14:41 ` Peter Zijlstra
2015-06-23 12:20 ` Vineet Gupta
2015-06-17 12:32 ` Vineet Gupta
2015-06-09 12:19 ` [PATCH 2/8] ARC: perf: cap the number of counters to hardware max of 32 Vineet Gupta
2015-06-09 12:19 ` [PATCH 3/8] ARCv2: perf: implement "event_set_period" for future use with interrupts Vineet Gupta
2015-06-15 15:38 ` Peter Zijlstra
2015-06-22 15:26 ` Alexey Brodkin
2015-06-09 12:19 ` [PATCH 4/8] ARCv2: perf: Support sampling events using overflow interrupts Vineet Gupta
2015-06-15 15:48 ` Peter Zijlstra [this message]
2015-06-22 15:57 ` Alexey Brodkin
2015-06-15 16:25 ` Peter Zijlstra
2015-06-16 5:37 ` Vineet Gupta
2015-06-16 9:07 ` Peter Zijlstra
2015-06-16 9:33 ` Vineet Gupta
2015-06-17 11:48 ` Vineet Gupta
2015-06-17 12:44 ` Peter Zijlstra
2015-06-09 12:19 ` [PATCH 5/8] ARCv2: perf: set usable max period as a half of real max period Vineet Gupta
2015-06-09 12:19 ` [PATCH 6/8] ARCv2: perf: implement exclusion of event counting in user or kernel mode Vineet Gupta
2015-06-09 12:19 ` [PATCH 7/8] ARCv2: perf: SMP support Vineet Gupta
2015-06-09 12:19 ` [PATCH 8/8] ARCv2: perf: Finally introduce HS perf unit Vineet Gupta
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