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    Contents of /alx-src/trunk/kernel26-alx/linux/Documentation/IRQ-affinity.txt

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    Revision 628 - (show annotations) (download)
    Wed Mar 4 10:48:58 2009 UTC (15 years, 1 month ago) by niro
    File MIME type: text/plain
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    import linux sources based on 2.6.12-alx-r9:
 -using linux-2.6.12.6
 -using 2.6.12-ck6 patch set
 -using fbsplash-0.9.2-r3
 -using vesafb-tng-0.9-rc7
 -using squashfs-2.2
 -added cddvd-cmdfilter-drop.patch as ck dropped it
 -added via-epia-dri (cle266) patch
 -added zd1211-svn-32 wlan driver (http://zd1211.ath.cx/download/)
 -added debian patches to zd1211 for wep256 etc
    1
    2 SMP IRQ affinity, started by Ingo Molnar <mingo@redhat.com>
    3
    4
    5 /proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted
    6 for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed
    7 to turn off all CPUs, and if an IRQ controller does not support IRQ
    8 affinity then the value will not change from the default 0xffffffff.
    9
    10 Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting
    11 the IRQ to CPU4-7 (this is an 8-CPU SMP box):
    12
    13 [root@moon 44]# cat smp_affinity
    14 ffffffff
    15 [root@moon 44]# echo 0f > smp_affinity
    16 [root@moon 44]# cat smp_affinity
    17 0000000f
    18 [root@moon 44]# ping -f h
    19 PING hell (195.4.7.3): 56 data bytes
    20 ...
    21 --- hell ping statistics ---
    22 6029 packets transmitted, 6027 packets received, 0% packet loss
    23 round-trip min/avg/max = 0.1/0.1/0.4 ms
    24 [root@moon 44]# cat /proc/interrupts | grep 44:
    25 44: 0 1785 1785 1783 1783 1
    26 1 0 IO-APIC-level eth1
    27 [root@moon 44]# echo f0 > smp_affinity
    28 [root@moon 44]# ping -f h
    29 PING hell (195.4.7.3): 56 data bytes
    30 ..
    31 --- hell ping statistics ---
    32 2779 packets transmitted, 2777 packets received, 0% packet loss
    33 round-trip min/avg/max = 0.1/0.5/585.4 ms
    34 [root@moon 44]# cat /proc/interrupts | grep 44:
    35 44: 1068 1785 1785 1784 1784 1069 1070 1069 IO-APIC-level eth1
    36 [root@moon 44]#
    37