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From: "Gregory Haskins" <ghaskins@novell.com>
To: "Steven Rostedt" <rostedt@goodmis.org>
Cc: <a.p.zijlstra@chello.nl>, <mingo@elte.hu>, <bill.huey@gmail.com>,
	<kevin@hilman.org>, <tglx@linutronix.de>, <cminyard@mvista.com>,
	<dsingleton@mvista.com>, <dwalker@mvista.com>,
	"Moiz Kohari" <MKohari@novell.com>,
	"Peter Morreale" <PMorreale@novell.com>,
	"Sven Dietrich" <SDietrich@novell.com>, <dsaxena@plexity.net>,
	<acme@redhat.com>, <ak@suse.de>, <gregkh@suse.de>,
	<npiggin@suse.de>, <pavel@ucw.cz>, <linux-kernel@vger.kernel.org>,
	<linux-rt-users@vger.kernel.org>
Subject: Re: [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing to includelateral priority
Date: Mon, 03 Mar 2008 08:41:17 -0700	[thread overview]
Message-ID: <47CBD5CD.BA47.005A.0@novell.com> (raw)
In-Reply-To: <Pine.LNX.4.58.0803030944530.18766@gandalf.stny.rr.com>

>>> On Mon, Mar 3, 2008 at 10:13 AM, in message
<Pine.LNX.4.58.0803030944530.18766@gandalf.stny.rr.com>, Steven Rostedt
<rostedt@goodmis.org> wrote: 


> 
> See the issue. The RT task on CPU0 may experience huge latencies.

Agreed, but equal priority threads can always cause unbounded latencies by definition.  I.e. we only guarantee to the highest thread.

> Remember, RT is worried about latencies over performance.
> If we can not ***guarantee*** a bounded latency, then, I don't care
> how good the perfomance is, it is not good enough for RT.
> 
> 
> That said, here's the compromise.
> 
> Non-RT tasks care more about overall perfomance than worst case latencies.
> So.... See imbedded:

This isn't a bad idea, but note that it means RT tasks will not get a performance boost, which is quite substantial.

Note that I have substantially cleaned up this patch for the drop I will make later this week (v3).

-Greg


  reply	other threads:[~2008-03-03 15:48 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-25 16:00 [(RT RFC) PATCH v2 0/9] adaptive real-time locks Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing to include lateral priority Gregory Haskins
2008-03-03 15:13   ` Steven Rostedt
2008-03-03 15:41     ` Gregory Haskins [this message]
2008-03-03 15:55       ` [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing to includelateral priority Steven Rostedt
2008-03-03 15:55         ` [(RT RFC) PATCH v2 1/9] allow rt-mutex lock-stealing toincludelateral priority Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 2/9] sysctl for runtime-control of lateral mutex stealing Gregory Haskins
2008-02-25 21:53   ` Pavel Machek
2008-02-25 22:57     ` Sven-Thorsten Dietrich
2008-02-25 23:00       ` Pavel Machek
2008-02-25 23:40         ` Sven-Thorsten Dietrich
2008-02-26  1:15       ` Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 3/9] rearrange rt_spin_lock sleep Gregory Haskins
2008-02-25 21:54   ` Pavel Machek
2008-02-26  0:45     ` Gregory Haskins
2008-02-25 16:00 ` [(RT RFC) PATCH v2 4/9] optimize rt lock wakeup Gregory Haskins
2008-03-03 15:37   ` Steven Rostedt
2008-03-03 15:41     ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 5/9] adaptive real-time lock support Gregory Haskins
2008-02-25 22:03   ` Pavel Machek
2008-02-26  0:48     ` Gregory Haskins
2008-02-26 15:03     ` Gregory Haskins
2008-02-26 18:06       ` Pavel Machek
2008-02-26 18:01         ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 6/9] add a loop counter based timeout mechanism Gregory Haskins
2008-02-25 22:06   ` Pavel Machek
2008-02-25 22:19     ` Greg KH
2008-02-25 22:21       ` Pavel Machek
2008-02-25 22:39     ` Sven-Thorsten Dietrich
2008-02-26 15:09     ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 7/9] adaptive mutexes Gregory Haskins
2008-02-25 22:09   ` Pavel Machek
2008-02-26  0:52     ` Gregory Haskins
2008-02-25 16:01 ` [(RT RFC) PATCH v2 8/9] adjust pi_lock usage in wakeup Gregory Haskins
2008-02-25 22:10   ` Pavel Machek
2008-02-25 16:01 ` [(RT RFC) PATCH v2 9/9] remove the extra call to try_to_take_lock Gregory Haskins

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