Re: [PATCH V3] x86, UV: BAU performance and error recovery

[Cliff Wickman <cpw@sgi.com>]

On Fri, May 28, 2010 at 05:10:20PM -0700, JD wrote:
>
>
> On 05/28/2010 04:36 PM, Cliff Wickman wrote:
>> On Fri, May 28, 2010 at 03:23:21PM -0700, Greg KH wrote:
>>    
>>> On Fri, May 28, 2010 at 02:43:35PM -0500, Cliff Wickman wrote:
>>>      
>>>> On Fri, May 28, 2010 at 09:47:25AM -0700, Greg KH wrote:
>>>>        
>>>>> On Fri, May 28, 2010 at 09:30:25AM -0700, H. Peter Anvin wrote:
>>>>>          
>>>>>> On 05/28/2010 06:33 AM, Cliff Wickman wrote:
>>>>>>            
>>>>>>> - adds modification of tuning variables through /proc/sgi_uv
>>>>>>>              
>>>>>> Adding new directories in /proc for a proprietary architecture is
>>>>>> frowned upon, to put it mildly.  At the very least try to find a place
>>>>>> in sysfs for it.
>>>>>>
>>>>>> [Cc: gregkh in order to find a place in sysfs]
>>>>>>            
>>>>> Hm, what type of files are you needing here?  Do they corrispond with
>>>>> any specific hardware devices?  If so, just put them on the hardware
>>>>> devices in sysfs.
>>>>>
>>>>> thanks,
>>>>>
>>>>> greg k-h
>>>>>          
>>>> There is an SGI-specific directory in sysfs: /sys/firmware/sgi_uv
>>>> though the tuning variables for the handling of the hardware Broadcast
>>>> Assist Unit don't fit there very logically.
>>>>
>>>> The BAU's statistics are already displayed through the UV-only
>>>> /proc/sgi_uv/ptc_statistics.  This was deemed necessary because of the
>>>> potentially very large size of that file --- it is still true that a /sys file
>>>> is limited to one page, is it not?
>>>>        
>>> It is limited to one single value, which would never be larger than a
>>> page, so yes, it is limited to one page.
>>>
>>> What kind of information are you showing here?  Should this thing just
>>> be in debugfs instead?  You can do whatever you want there.
>>>
>>> thanks,
>>>
>>> greg k-h
>>>      
>> /proc/sgi_uv/bau_tunables would be a read/write file to display and change
>> nine threshold and delay values for tuning the BAU driver.
>>
>> I like debugfs, except that a distro may not build the kernel with it
>> configured on.  The tunables should be available as administrative
>> options on a customer kernel, not just as a development tool.
>>
>> And in our case the distros are already building with other such writable
>> options in /proc/sgi_uv.  We'd like to postpone a wholesale move of such
>> options (assuming there will be some better place) and stay with the existing
>> location for this release.
>>
>> I know we (the community) would like to move non-process info out of /proc.
>> It seems to me that we need a similar filesystem for large and/or
>> administrative files.  That's my perspective.
>>
>> -Cliff
>>    
> Would the similar filesystem you propose be backed by permanent storage,  
> unlike /proc?

I withdraw my proposal for any new filesystem type, as debugfs works fine
for what I'm talking about, as long as it is configured on by all the
distributions.
No, a permanent storage backed filesystem was not what I had in mind.

-- 
Cliff Wickman
SGI
cpw@sgi.com
(651) 683-3824