* [Xenomai-help] Strange issue : high latency for kernel task when a user task is stop [not found] <71396b5b0910010109h5cb5912el7eee9d071ed23cda@domain.hid> @ 2009-10-02 7:21 ` Gilles FRITZ 2009-10-02 7:36 ` Gilles Chanteperdrix 0 siblings, 1 reply; 2+ messages in thread From: Gilles FRITZ @ 2009-10-02 7:21 UTC (permalink / raw) To: xenomai [-- Attachment #1: Type: text/plain, Size: 649 bytes --] Hi, I use Xenomai since not very long, but I have seen a strange behavior : when I stop a user-space task, my in-kernel task have a latency of about 500µs. I have observed that on Xenomai 2.4.8 and 2.3.4, on kernel 2.6.25.19 and 2.6.28.9. To observe that, I launch two latency test : one in user-space and the second in kernel-space latency -p 50 -t 1 latency -p 70 When I stop the second latency (in user-space), I can observe a latency of at least 500ms in the in-kernel task. I do not know if this is normal or not. Have you an explanation for that? -- Regards, Gilles FRITZ -- Cordialement, Gilles FRITZ [-- Attachment #2: Type: text/html, Size: 797 bytes --] ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Xenomai-help] Strange issue : high latency for kernel task when a user task is stop 2009-10-02 7:21 ` [Xenomai-help] Strange issue : high latency for kernel task when a user task is stop Gilles FRITZ @ 2009-10-02 7:36 ` Gilles Chanteperdrix 0 siblings, 0 replies; 2+ messages in thread From: Gilles Chanteperdrix @ 2009-10-02 7:36 UTC (permalink / raw) To: Gilles FRITZ; +Cc: xenomai Gilles FRITZ wrote: > Hi, > > I use Xenomai since not very long, but I have seen a strange behavior : when > I stop a user-space task, my in-kernel task have a latency of about 500µs. > > I have observed that on Xenomai 2.4.8 and 2.3.4, on kernel 2.6.25.19 and > 2.6.28.9. > > To observe that, I launch two latency test : one in user-space and the > second in kernel-space > latency -p 50 -t 1 > latency -p 70 > > When I stop the second latency (in user-space), I can observe a latency of > at least 500ms in the in-kernel task. > > I do not know if this is normal or not. > > Have you an explanation for that? I do not think we have but: - 50us and 70us are a bit short periods depending on the platform (though it should not change anything to use larger periods), and you did not tell us on what platform you are running xenomai - the I-pipe patch proposes an option, the I-pipe tracer, which will tell you exactly what happens during these 500us. -- Gilles. ^ permalink raw reply [flat|nested] 2+ messages in thread
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2009-10-02 7:21 ` [Xenomai-help] Strange issue : high latency for kernel task when a user task is stop Gilles FRITZ
2009-10-02 7:36 ` Gilles Chanteperdrix
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