From: Bill Davidsen <davidsen@tmr.com>
To: Lee Revell <rlrevell@joe-job.com>
Cc: Zwane Mwaikambo <zwane@arm.linux.org.uk>,
"Luck, Tony" <tony.luck@intel.com>,
Tony Luck <tony.luck@gmail.com>, Andrew Morton <akpm@osdl.org>,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
Jack Steiner <steiner@sgi.com>, Keith Owens <kaos@sgi.com>,
Dimitri Sivanich <sivanich@sgi.com>
Subject: Re: [PATCH] ia64: disable preemption in udelay()
Date: Thu, 22 Dec 2005 16:45:08 -0500 [thread overview]
Message-ID: <43AB1E64.6010504@tmr.com> (raw)
In-Reply-To: <1134703152.12086.231.camel@mindpipe>
Lee Revell wrote:
> On Thu, 2005-12-15 at 18:12 -0800, John Hawkes wrote:
>
>>From: "Lee Revell" <rlrevell@joe-job.com>
>>
>>>There are 10 drivers that udelay(10000) or more and a TON that
>>>udelay(1000). Turning those all into 1ms+ non preemptible sections will
>>>be very bad.
>>
>>What about 100usec non-preemptible sections?
>
>
> That will disappear into the noise, in normal usage these happen all the
> time. 500usec non preemptible regions are rare (~1 hour to show up) and
> 1ms very rare (24 hours). My tests show that 300 usec or so is a good
> place to draw the line if you don't want it to show up in latency tests.
I may be misreading the original post, but the problem is described as
one where the TSC is not syncronised and a CPU switch takes place. Would
the correct solution be to somehow set CPU affinity temporarily in such
a way as to avoid disabling preempt at all?
The preempt doesn't seem to be the root problem, so it's unlikely to be
the best solution...
--
-bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
next prev parent reply other threads:[~2005-12-22 21:45 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-14 23:25 [PATCH] ia64: disable preemption in udelay() hawkes
2005-12-15 22:50 ` Luck, Tony
2005-12-16 1:04 ` Luck, Tony
2005-12-16 8:20 ` Christian Hildner
2005-12-16 14:14 ` Alan Cox
2005-12-16 1:52 ` Zwane Mwaikambo
2005-12-16 2:03 ` Lee Revell
2005-12-16 2:12 ` John Hawkes
2005-12-16 2:40 ` Zwane Mwaikambo
2005-12-16 3:19 ` Lee Revell
2005-12-22 21:45 ` Bill Davidsen [this message]
2005-12-23 0:14 ` Keith Owens
2005-12-23 6:03 ` Zwane Mwaikambo
2005-12-16 2:37 ` Zwane Mwaikambo
2005-12-16 2:42 hawkes
2005-12-16 12:28 ` Robin Holt
2005-12-16 17:33 ` Luck, Tony
2005-12-16 18:39 ` John Hawkes
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