On Wed, Dec 3, 2014 at 2:20 PM, Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx> wrote: > On Wed, 3 Dec 2014 14:08:01 -0500 > Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote: >> Which workqueue are you using? Since the receive code is non-blocking, >> I'd expect you might be able to use rpciod, for the initial socket >> reads, but you wouldn't want to use that for the actual knfsd >> processing. >> > > I'm using the same (nfsd) workqueue for everything. The workqueue > isn't really the bottleneck though, it's the work_struct. > > Basically, the problem is that the work_struct in the svc_xprt was > remaining busy for far too long. So, even though the XPT_BUSY bit had > cleared, the work wouldn't get picked up again until the previous > workqueue job had returned. > > With the change I made today, I just added a new work_struct to > svc_rqst and queue that to the same workqueue to do svc_process as soon > as the receive is done. That means though that each RPC ends up waiting > in the queue twice (once to do the receive and once to process the > RPC), and I think that's probably the reason for the performance delta. Why would the queuing latency still be significant now? > What I think I'm going to do on the next pass is have the job that > enqueues the xprt instead try to find an svc_rqst. If it finds it, > then it can go ahead and queue the work struct in it to do the receive > and processing in a single go. > > If it can't find one, it'll queue the xprt's work to allocate one and > then queue that to do all of the work as before. That will likely > penalize the case where there isn't an available svc_rqst, but in the > common case that there is one it should go quickly. -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
