From: llandre <r&d2-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org>
To: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: spi_async and heavy CPU occupation by ksoftirqd
Date: Wed, 08 Aug 2007 10:21:21 +0200 [thread overview]
Message-ID: <46B97D01.5000208@dave-tech.it> (raw)
I'm facing the following problem.
I have to poll a SPI device periodically (around ten times a second).
Both command and response are 1 byte. To do the job I created a work
that looks like this:
work(...)
{
sets debug_pin
poll the device
err = queue_delayed_work(wq, work, (HZ / 10));
clears debug_pin
}
The actual SPI transaction is perfomed by invoking spi_async. SPI
transactions work fine but the kernel daemon ksoftirqd eats about 18% of
CPU time. With the help of debug pin, I measured the execution time of
function work that is around 70us. Then I commented out the call of
spi_async and the ksoftirqd CPU occupation drops to 0%. Am I doing
something wrong?
I'm working with kernel 2.6.21.3 on iMXL ARM9 processor.
TIA,
llandre
DAVE Electronics System House - R&D Department
web: http://www.dave-tech.it
email: r&d2-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org
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next reply other threads:[~2007-08-08 8:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-08 8:21 llandre [this message]
[not found] ` <46B97D01.5000208-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org>
2007-08-08 16:27 ` spi_async and heavy CPU occupation by ksoftirqd David Brownell
[not found] ` <200708080927.36737.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2007-08-09 14:05 ` llandre
[not found] ` <46BB1F10.3030608-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org>
2007-08-09 15:23 ` David Brownell
[not found] ` <200708090823.29708.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2007-08-10 8:52 ` llandre
[not found] ` <46BC2732.5070504-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org>
2007-08-10 10:29 ` Andrea Paterniani
[not found] ` <FLEPLOLKEPNLMHOILNHPMEKGDKAA.a.paterniani-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>
2007-08-10 11:32 ` llandre
[not found] ` <46BC4CD3.5090304-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org>
2007-08-10 12:27 ` R: " Andrea Paterniani
[not found] ` <FLEPLOLKEPNLMHOILNHPIEKIDKAA.a.paterniani-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>
2007-08-14 8:29 ` llandre
[not found] ` <46C167F0.4040100-4VKA1VU3ct/j+vYz1yj4TQ@public.gmane.org>
2007-08-14 9:43 ` llandre
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