On Mon, 2012-10-08 at 15:59 -0400, Andy Adamson wrote:
> On Mon, Oct 8, 2012 at 1:50 PM, Trond Myklebust
> <Trond.Myklebust@xxxxxxxxxx> wrote:
> > Aside from it being a layering violation, there is no point in doing so:
> > - If slots are available, then the waitqueue will be empty.
> > - If no slots are available, then the wake up just causes waitqueue churn
>
> We call rpc_wake_up so that I/O waiting on the DS session, all of
> which needs to be re-directed to the MDS (not via the state recovery
> machinery), will by-pass the RPC machine "try each task one at a time
> and redirect on failure" which includes the 60 second TCP timeout on
> DS connection failures.
>
> So, it doesn't just cause waitqueue churn, it significantly reduces
> the time it takes to recover to the MDS.
>
All it does is a wake up... That will happen _ANYWAY_ as soon as a slot
is made available.
So yes, it is pure churn...
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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