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Message-ID: <20150108115117.GK3337@twins.programming.kicks-ass.net>
Date: Thu, 8 Jan 2015 12:51:17 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Matt Fleming <matt@...sole-pimps.org>
Cc: Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Andi Kleen <andi@...stfloor.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
Kanaka Juvva <kanaka.d.juvva@...el.com>,
Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH 11/11] perf/x86/intel: Enable conflicting event
scheduling for CQM
On Fri, Nov 14, 2014 at 09:15:12PM +0000, Matt Fleming wrote:
> +/*
> + * Deallocate the RMIDs from any events that conflict with @event, and
> + * place them on the back of the group list.
> + */
> +static void intel_cqm_sched_out_events(struct perf_event *event)
> +{
> + struct perf_event *group, *g;
> + unsigned int rmid;
>
> + lockdep_assert_held(&cache_mutex);
> +
> + list_for_each_entry_safe(group, g, &cache_groups, hw.cqm_groups_entry) {
> + if (group == event)
> + continue;
> +
> + rmid = group->hw.cqm_rmid;
> +
> + /*
> + * Skip events that don't have a valid RMID.
> + */
> + if (!__rmid_valid(rmid))
> + continue;
> +
> + /*
> + * No conflict? No problem! Leave the event alone.
> + */
> + if (!__conflict_event(group, event))
> + continue;
> +
> + intel_cqm_xchg_rmid(group, INVALID_RMID);
> + __put_rmid(rmid);
> +
> + list_move_tail(&group->hw.cqm_groups_entry, &cache_groups);
> + }
> }
I'm not sure about that list_move_tail() there, is wrecks the rotation
order and would cause conflicting events to get less than their 'fair'
share I suspect.
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