Re: [PATCH v4 0/4] Sending kernel pathrecord query to user cache server

[Hal Rosenstock <hal-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 6/10/2015 10:22 AM, Wan, Kaike wrote:
> 
> 
>> -----Original Message-----
>> From: Hal Rosenstock [mailto:hal-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org]
>> Sent: Wednesday, June 10, 2015 9:37 AM
>>
>>>
>>> A SA cache is undeniably critical for fabric scalability and performance.
>>> In user space, the ibacm application provides a good example of
>>> pathrecord cache for address and route resolution. With the recent
>>> implementation of the provider architecture, ibacm offers more
>> extensibility as a SA cache.
>>> In kernel, ipoib implements its own small cache for pathrecords, which
>>> is however not available for general use. Furthermore, the
>>> implementation of a SA cache in user space offers better flexibility,
>>> larger capacity, and more robustness for the system.
>>>
>>> In this patch series, a mechanism is implemented to allow ib_sa to
>>> send pathrecord query to a user application (eg ibacm) through netlink.
>>
>> While this appears to address the current upstream use model for ACM with
>> it's multicast overlay backend where PRs are static, it does not appear to
>> address PR changes.
>> Should aging/revalidation of PRs be supported ? If so, would this make PRs
>> similar at "high" level to IP neighbor cache in kernel ?
> 
> Even for the default provider acmp, PRs will time out and the length of timeout is configurable. For other providers (eg ibssa), the PR change could be managed correctly and promptly, and this capability is beyond ibacm core itself. 

That deals with the update of PR in user space (ACM). Doesn't kernel
need some way of knowing PR was updated ?

-- Hal

> Kaike
> 
> 

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