From: Peter Zijlstra <peterz@infradead.org>
To: Xunlei Pang <xlpang@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Juri Lelli <juri.lelli@arm.com>, Ingo Molnar <mingo@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v2 2/2] rtmutex: Kill pi_waiters_leftmost from task_struct
Date: Wed, 6 Apr 2016 20:15:29 +0200 [thread overview]
Message-ID: <20160406181529.GU3448@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1459947556-12332-2-git-send-email-xlpang@redhat.com>
On Wed, Apr 06, 2016 at 08:59:16PM +0800, Xunlei Pang wrote:
> Current code use pi_waiters_leftmost to record the leftmost waiter,
> but actually it can be get directly from task_struct::pi_waiters
> using rb_first(). The performance penalty introduced by rb_first()
> should be fine, because normally there aren't that many rtmutexes
> chained together for one task.
>
> We don't remove rt_mutex:pi_waiters_leftmost, as it is quite possible
> for many tasks sharing one rtmutex.
>
> Thus, hereby remove pi_waiters_leftmost from task_struct.
Again, I would like Thomas to chime in. This isn't about usual, but very
much about worst case performance -- its RT code after all.
next prev parent reply other threads:[~2016-04-06 18:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-06 12:59 [PATCH v2 1/2] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Xunlei Pang
2016-04-06 12:59 ` [PATCH v2 2/2] rtmutex: Kill pi_waiters_leftmost from task_struct Xunlei Pang
2016-04-06 18:15 ` Peter Zijlstra [this message]
2016-04-06 18:14 ` [PATCH v2 1/2] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra
2016-04-08 8:04 ` Xunlei Pang
2016-04-08 8:31 ` Peter Zijlstra
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