From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <jolsa@kernel.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>, Andi Kleen <andi@firstfloor.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Vince Weaver <vince@deater.net>
Subject: Re: [PATCH 4/4] perf/x86/intel: Throttle PEBS events only from pmi
Date: Tue, 3 Jan 2017 14:45:25 +0100 [thread overview]
Message-ID: <20170103134525.GW3107@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1482931866-6018-5-git-send-email-jolsa@kernel.org>
On Wed, Dec 28, 2016 at 02:31:06PM +0100, Jiri Olsa wrote:
> This patch fixes following WARNING:
>
> WARNING: CPU: 15 PID: 15768 at arch/x86/events/core.c:1256 x86_pmu_start+0x1b3/0x1c0
> ...
> Call Trace:
> <IRQ>
> dump_stack+0x86/0xc3
> __warn+0xcb/0xf0
> warn_slowpath_null+0x1d/0x20
> x86_pmu_start+0x1b3/0x1c0
> perf_event_task_tick+0x342/0x3f0
> scheduler_tick+0x75/0xd0
> update_process_times+0x47/0x60
> tick_sched_handle.isra.19+0x25/0x60
> tick_sched_timer+0x3d/0x70
> __hrtimer_run_queues+0xfb/0x510
> hrtimer_interrupt+0x9d/0x1a0
> local_apic_timer_interrupt+0x38/0x60
> smp_trace_apic_timer_interrupt+0x56/0x25a
> trace_apic_timer_interrupt+0x9d/0xb0
> ...
>
> which happens AFAICS under following conditions:
> (we have PEBS events configured)
>
> - x86_pmu_enable reconfigures counters and calls:
> - x86_pmu_stop on PEBS event
> - x86_pmu_stop drains the PEBS buffer, crosses
> the throttle limit and sets:
> event->hw.interrupts = MAX_INTERRUPTS
> - following x86_pmu_start call starts the event
> - perf_event_task_tick is triggered
> - perf_adjust_freq_unthr_context sees event with
> MAX_INTERRUPTS set and calls x86_pmu_start on already
> started event, which triggers the warning
>
> My first attempt to fix this was to unthrottle the event
> before starting it in x86_pmu_enable. But I think that
> omitting the throttling completely when we are not in the
> PMI is better.
Hurm,.. good catch that. Makes a bit of a mess of things though. Then
again, I cannot quickly think of something better either :/
next prev parent reply other threads:[~2017-01-03 13:46 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-28 13:31 [PATCH 0/4] perf: Fuzzer fixes Jiri Olsa
2016-12-28 13:31 ` [PATCH 1/4] perf/x86/intel: Account interrupts for PEBS errors Jiri Olsa
2017-01-14 12:29 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2016-12-28 13:31 ` [PATCH 2/4] perf/x86: Fix period for non sampling events Jiri Olsa
2017-01-03 9:40 ` Peter Zijlstra
2017-01-03 14:24 ` [PATCH] perf/x86: Reject non sampling events with precise_ip Jiri Olsa
2017-01-03 22:06 ` Vince Weaver
2017-01-14 12:29 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2017-01-03 15:09 ` [PATCH 2/4] perf/x86: Fix period for non sampling events Peter Zijlstra
2017-01-03 15:26 ` Jiri Olsa
2016-12-28 13:31 ` [PATCH 3/4] perf: Add perf_event_overflow_throttle function Jiri Olsa
2016-12-28 13:31 ` [PATCH 4/4] perf/x86/intel: Throttle PEBS events only from pmi Jiri Olsa
2017-01-03 13:45 ` Peter Zijlstra [this message]
2017-01-24 16:41 ` Peter Zijlstra
2017-01-25 13:02 ` Jiri Olsa
2017-01-25 13:02 ` Jiri Olsa
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