linux-kernel - Re: [RFC PATCH 00/14] nfsd/sunrpc: add support for a workqueue-based nfsd

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Message-ID: <54809D7F.4020901@oracle.com>
Date:	Thu, 04 Dec 2014 09:44:31 -0800
From:	Shirley Ma <shirley.ma@...cle.com>
To:	Jeff Layton <jeff.layton@...marydata.com>
CC:	Trond Myklebust <trond.myklebust@...marydata.com>,
	Tejun Heo <tj@...nel.org>, NeilBrown <neilb@...e.de>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Kernel mailing list <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC PATCH 00/14] nfsd/sunrpc: add support for a workqueue-based
 nfsd

On 12/04/2014 09:28 AM, Jeff Layton wrote:
> On Thu, 04 Dec 2014 09:17:17 -0800
> Shirley Ma <shirley.ma@...cle.com> wrote:
> 
>> > I am looking at how to reduce total RPC execution time in NFS/RDMA. mountstats output shows that RPC backlog wait is too long, but increasing the credit limit doesn't seem help. Would this patchset help reducing total RPC execution time? 
>> > 
>> > Shirley
>> > 
> I'm not sure. It depends on why you're seeing a backlog.

What's the major factors contributing RPC backlog wait time? I guess I need to probe the backlog wait path to display fine-grained latency cost.
 
> So far, my testing still shows this to be slightly (~2%) slower than the
> same setup running a threaded nfsd, but that could be different with a
> NUMA server or faster disks.
> 
> Probably there is some more tuning to do here before this is quite
> ready for prime-time. It may be worth testing in your environment
> though if you have the time and ability to do so.
> 
>> > On 12/04/2014 03:47 AM, Jeff Layton wrote:
>>> > > I was using ftrace with the sunrpc:* and workqueue:* tracepoints, and
>>> > > had a simple perl script to postprocess the trace info to figure out
>>> > > average/min/max latency.
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