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SubjectRe: [PATCH] bitmap, irq: Add smp_affinity_list interface to /proc/irq
On Tue, 29 Mar 2011 17:51:18 -0700 Mike Travis <travis@sgi.com> wrote:

> >
> > Also, the patch adds a new interface which duplicates an existing one,
> > only the formats are different, yes? This is, of course, bad.
> >
> > The only justification we've seen for being bad is "Manually adjusting
> > the smp_affinity for IRQ's becomes unwieldy when the cpu count is
> > large". A more thorough description of how painful this is might help
> > motivate people to do bad things to the kernel.
> >
> > Also, if it's just a matter of an alternative presentation of the data,
> > why not implement the desired user interface with a little userspace
> > tool then feed the results down into the existing kernel interface?
> >
>
> Setting smp affinity to cpus 256 to 263 would be:
>
> echo 000000ff,00000000,00000000,00000000,00000000,00000000,00000000,00000000 > smp_affinity
>
> instead of:
>
> echo 256-263 > smp_affinity_list
>
> Think about what it looks like for cpus around say, 4088 to 4095.
>
> We already have many alternate "list" interfaces:
>
> /sys/devices/system/cpu/cpuX/indexY/shared_cpu_list
> /sys/devices/system/cpu/cpuX/topology/thread_siblings_list
> /sys/devices/system/cpu/cpuX/topology/core_siblings_list
> /sys/devices/system/node/nodeX/cpulist
> /sys/devices/pci***/***/local_cpulist
>
> etc.
>
> This just expands on that same philosophy.

You mean that if someone had written a stupid little tool to convert a
list of tuples into a bitmap, we wouldn't have needed to add all that
crap to the kernel?



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