diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/IRQ-affinity.txt | 17 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.txt | 11 |
2 files changed, 22 insertions, 6 deletions
diff --git a/Documentation/IRQ-affinity.txt b/Documentation/IRQ-affinity.txt index b4a615b..7890fae 100644 --- a/Documentation/IRQ-affinity.txt +++ b/Documentation/IRQ-affinity.txt @@ -4,10 +4,11 @@ ChangeLog: SMP IRQ affinity -/proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted -for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed -to turn off all CPUs, and if an IRQ controller does not support IRQ -affinity then the value will not change from the default 0xffffffff. +/proc/irq/IRQ#/smp_affinity and /proc/irq/IRQ#/smp_affinity_list specify +which target CPUs are permitted for a given IRQ source. It's a bitmask +(smp_affinity) or cpu list (smp_affinity_list) of allowed CPUs. It's not +allowed to turn off all CPUs, and if an IRQ controller does not support +IRQ affinity then the value will not change from the default of all cpus. /proc/irq/default_smp_affinity specifies default affinity mask that applies to all non-active IRQs. Once IRQ is allocated/activated its affinity bitmask @@ -54,3 +55,11 @@ round-trip min/avg/max = 0.1/0.5/585.4 ms This time around IRQ44 was delivered only to the last four processors. i.e counters for the CPU0-3 did not change. +Here is an example of limiting that same irq (44) to cpus 1024 to 1031: + +[root@moon 44]# echo 1024-1031 > smp_affinity +[root@moon 44]# cat smp_affinity +1024-1031 + +Note that to do this with a bitmask would require 32 bitmasks of zero +to follow the pertinent one. diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 60740e8..f481780 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -574,6 +574,12 @@ The contents of each smp_affinity file is the same by default: > cat /proc/irq/0/smp_affinity ffffffff +There is an alternate interface, smp_affinity_list which allows specifying +a cpu range instead of a bitmask: + + > cat /proc/irq/0/smp_affinity_list + 1024-1031 + The default_smp_affinity mask applies to all non-active IRQs, which are the IRQs which have not yet been allocated/activated, and hence which lack a /proc/irq/[0-9]* directory. @@ -583,12 +589,13 @@ reports itself as being attached. This hardware locality information does not include information about any possible driver locality preference. prof_cpu_mask specifies which CPUs are to be profiled by the system wide -profiler. Default value is ffffffff (all cpus). +profiler. Default value is ffffffff (all cpus if there are only 32 of them). The way IRQs are routed is handled by the IO-APIC, and it's Round Robin between all the CPUs which are allowed to handle it. As usual the kernel has more info than you and does a better job than you, so the defaults are the -best choice for almost everyone. +best choice for almost everyone. [Note this applies only to those IO-APIC's +that support "Round Robin" interrupt distribution.] There are three more important subdirectories in /proc: net, scsi, and sys. The general rule is that the contents, or even the existence of these |
