[openib-general] Re: Re: [PATCH 0/4] SA path record caching

[Michael S. Tsirkin]

Quoting r. Sean Hefty <mshefty at ichips.intel.com>:
> Subject: Re: Re: [PATCH 0/4] SA path record caching
> 
> Michael S. Tsirkin wrote:
> > When is the cache invalidated?
> 
> The cache is updated every 15 minutes, but this value is user configurable at 
> module load time.  The cache is also updated if a local event occurs, such as 
> port up/down or SM LID change.

Unfortunately port down on any link in the path has the same effect
but wont invalidate the cache.

One way to solve this would be to invalidate the cache, and retry,
if an attempt to connect to the remote node fails.

> > In the presence of failures in the network,
> > an attempt to create a connection with a cached path might fail.
> 
> The same is also true for paths returned directly from the SA, and detection of 
> the failure could depend on how often the SM sweeps the fabric.

SA gets trap notices on link failures, doesnt it?
So, unlike with the local cache, we dont depend on sweeps.

>  At some point, 
> the cache will contain multiple paths, letting the connection be retried along 
> another path.
> 
> - Sean
> 

Is this possible in the current implementation?

-- 
Michael S. Tsirkin
Staff Engineer, Mellanox Technologies