lkml.org 
[lkml]   [2011]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] bitmap, irq: Add smp_affinity_list interface to /proc/irq


Andrew Morton wrote:
> On Tue, 29 Mar 2011 16:56:12 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
>
>> On Tue, 29 Mar 2011 16:46:52 -0700
>> Mike Travis <travis@sgi.com> wrote:
>>
>>> + /* create /proc/irq/<irq>/smp_affinity_list */
>>> + proc_create_data("smp_affinity_list", 0600, desc->dir,
>>> + &irq_affinity_list_proc_fops, (void *)(long)irq);
>> Always document your interfaces, please. `grep -r smp_affinity
>> Documentation' shows where.
>>
>> And one we've seen a description of the proposed new interface, we can
>> review the patch!
>
> 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.

Thanks,
Mike


\
 
 \ /
  Last update: 2011-03-30 02:53    [W:0.189 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site