Sam Leffler wrote:
Eric van Gyzen wrote:
The irq and taskq for my ath(4) card often use excessive amounts of CPU
time, even when my network is idle. They are often above 10% and 15%,
respectively; occasionally, they are as high as 27% and 44%.
The system is an AMD Athlon64 2800+ running FreeBSD 6.2-RELEASE i386
with a custom kernel including the wlan_* stuff, ath, ath_hal, and
ath_rate_sample. It is a station using WPA2-PSK with AES-CCMP. The
access point is also a FreeBSD machine with an ath(4) card.
During periods of high CPU usage, the
rx failed 'cuz of PHY err
OFDM timing
fields of the athstats output are increasing rather quickly. For
example, while CPU usage was 25% and 46%, the OFDM timing field was
increasing by 43,000 per second.
Can anyone explain this? Is it a sign of failing hardware?
It means you're seeing lots of noise in the environment. The numbers
you cite are way too high (43K/sec is crazy) and the %cpu times see too
high for your processor but that's hard to evaluate. You don't indicate
what your h/w is (mac+phy) revs but presumably it's old enough that PHY
errors are not counted in h/w but instead sent to the host as little
packets that must be processed. If you actually use the radio you'll
see the error counts go down because the radio will be busy doing useful
work.
ath_hal: 0.9.17.2 (AR5210, AR5211, AR5212, RF5111, RF5112, RF2413, RF5413)
ath0: <Atheros 5212> mem 0xea100000-0xea10ffff irq 17 at device 9.0 on pci0
ath0: Ethernet address: 00:11:95:91:32:f4
ath0: mac 7.9 phy 4.5 radio 5.6
I also have a P3 1.0 GHz laptop running FreeBSD 6.2 with a CardBus ath card
with the same hardware revisions and configuration. When ath CPU usage is
high on the desktop, it's perfectly normal on the laptop (below 2%), even
when the two are only a meter apart. The CPU usage on the AP is also normal.
The desktop and AP have D-Link DWL-G520 cards; the laptop has a Netgear WG511T.
High phy error rates can also be caused by things like faulty antenna
connections and/or radio overload (i.e. sta and ap being too close
and/or using high power radios).
I put a different antenna on the desktop, with no change. The STA and AP
are about ten meters apart.
I can add a knob to the driver to turn off this stuff but then you will
likely see degraded performance as the PHY errors are used to tune the
baseband when there is noise and/or when the case temperature changes
(this can significantly affect radio operation).
I wouldn't ask you to do that, but thanks for offering.
I should also mention that the desktop occasionally reboots spontaneously,
as if I had hit the reset button. In particular, I wonder if the ath card
is flaking out. The wild CPU usage and spontaneous resets /might/ have
started around the same time, but I might be hallucinating.
Thanks for your help and education...and for writing the driver in the first
place.
Eric
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