From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <5050315D.8080107@xenomai.org> Date: Wed, 12 Sep 2012 08:53:17 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <504EC598.7050005@ebus.com> <504F8F55.9080006@xenomai.org> <504FAAE6.5010701@xenomai.org> In-Reply-To: <504FAAE6.5010701@xenomai.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Interpreting I-pipe trace List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Doug Brunner Cc: xenomai@xenomai.org On 09/11/2012 11:19 PM, Gilles Chanteperdrix wrote: > On 09/11/2012 09:21 PM, Gilles Chanteperdrix wrote: > >> On 09/11/2012 07:01 AM, Doug Brunner wrote: >> >>> While running my latency testing earlier I saw some rather high >>> worst-case latencies (~70us) compared to average case (~14us), so I ran >>> again with I-pipe tracing enabled. However, I'm not sure what to make of >>> the results. >>> >>> My worst case involves an IRQ (common_interrupt appears in the trace >>> with user value 0xFFFFFFC4) and the wiki page talks about being able to >>> translate the user value 0xFFFFFFF4 into IRQ 11 but doesn't elaborate on >>> how this correspondence works. I'm not horribly concerned since it's a >>> delay of 53 us on a rather slow processor (Geode LX800) but it would be >>> nice to know what interrupt is taking so long. >> >> >> You may also want to apply the following patch for SMI on Geode LX, and >> enable CONFIG_XENO_HW_SMI_WORKAROUND. You can remove the '#if 0', if you >> do not use PCI. > > > You have to pass cs5536.msr=1 to avoid using PCI registers access (which > use SMIs) in the IDE driver. > These two tricks seem to make a big difference here: http://sisyphus.hd.free.fr/~gilles/core-3.4-latencies/geode.png -- Gilles.