Hi,
I have board with MPC8572E (dual core PPC). I have one board running kernel
with IRQ_ALL_CPUS set to Y and another with that option turned off. Kernel
version #2.6.26
With IRQ_ALL_CPUS turned off
( Here interrupts all go to CPU0 )
hdparm -tT /dev/hda
/dev/hda:
Timing cached reads: 3048 MB in 2.00 seconds = 1523.79 MB/sec
Timing buffered disk reads: 10 MB in 3.07 seconds = 3.25 MB/sec
cat /proc/interrupts
CPU0 CPU1
18: 1394100 0 OpenPIC Edge ide0
With IRQ_ALL_CPUS turned on I see
(Here interrupts go to CPU0 and CPU1 )
hdparm -tT /dev/hda
/dev/hda:
Timing cached reads: 1076 MB in 2.00 seconds = 538.01 MB/sec
Timing buffered disk reads: 10 MB in 3.08 seconds = 3.25 MB/sec
cat /proc/interrupts
CPU0 CPU1
18: 44951 54765 OpenPIC Edge ide0
I "expected" that with IRQ_ALL_CPUS -- interrupt sharing I would be able to
get higher througput but I see things otherway around.
Would someone care to enlighten me as to why when I set IRQ_ALL_CPUS disk
I/O performance goes down so much? Under what circumstances should one then
turn on IRQ_ALL_CPUS option on PPC platform?
Regards,
/Subodh
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