Re: Pin-pointing the root of unusual application latencies
From: John Sigler
Date: Tue Jul 24 2007 - 05:20:42 EST
John Sigler wrote:
( check_dektec_in-1095 |#0): new 271 us user-latency.
( check_dektec_in-1095 |#0): new 275 us user-latency.
( check_dektec_in-1095 |#0): new 290 us user-latency.
( check_dektec_in-1095 |#0): new 297 us user-latency.
( check_dektec_in-1095 |#0): new 345 us user-latency.
( check_dektec_in-1095 |#0): new 358 us user-latency.
( check_dektec_in-1095 |#0): new 384 us user-latency.
( check_dektec_in-1095 |#0): new 392 us user-latency.
( check_dektec_in-1095 |#0): new 395 us user-latency.
( check_dektec_in-1095 |#0): new 396 us user-latency.
( check_dektec_in-1095 |#0): new 1031 us user-latency.
( check_dektec_in-1095 |#0): new 1100 us user-latency.
( check_dektec_in-1095 |#0): new 1105 us user-latency.
( check_dektec_in-1095 |#0): new 1106 us user-latency.
Here's the function trace for the 1106-µs latency:
http://linux.kernel.free.fr/latency/1106-us-trace.txt
The function trace for 400-µs latencies is different:
( check_dektec_in-1145 |#0): new 275 us user-latency.
( check_dektec_in-1145 |#0): new 276 us user-latency.
( check_dektec_in-1145 |#0): new 288 us user-latency.
( check_dektec_in-1145 |#0): new 289 us user-latency.
( check_dektec_in-1145 |#0): new 289 us user-latency.
( check_dektec_in-1145 |#0): new 290 us user-latency.
( check_dektec_in-1145 |#0): new 297 us user-latency.
( check_dektec_in-1145 |#0): new 345 us user-latency.
( check_dektec_in-1145 |#0): new 354 us user-latency.
( check_dektec_in-1145 |#0): new 377 us user-latency.
( check_dektec_in-1145 |#0): new 393 us user-latency.
http://linux.kernel.free.fr/latency/393-us-trace.txt
There are ~200 calls to ioread32 from mdio_read from speedo_timer.
http://lxr.linux.no/source/drivers/net/eepro100.c#L1159
http://lxr.linux.no/source/drivers/net/eepro100.c#L928
In this case, and as far as I understand, the culprit is the eepro100
driver talking to one of the NICs (which one?). Is that correct?
What is the consequence of IRQ10 being shared by eth2 and
by my I/O board?
How can I force Linux to assign different IRQs to every peripheral
if I have free IRQs lines?
Regards.
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