Re: [PATCH] SUNRPC: Remove rpc_xprt::tsh_size

[Trond Myklebust <trondmy@hammerspace.com>]

On Thu, 2019-01-03 at 16:07 -0500, Chuck Lever wrote:
> > On Jan 3, 2019, at 3:53 PM, Chuck Lever <chuck.lever@oracle.com>
> > wrote:
> > 
> > > On Jan 3, 2019, at 1:47 PM, Trond Myklebust <
> > > trondmy@hammerspace.com> wrote:
> > > 
> > > On Thu, 2019-01-03 at 13:29 -0500, Chuck Lever wrote:
> > > > +	reclen = req->rq_snd_buf.len;
> > > > +	marker = cpu_to_be32(RPC_LAST_STREAM_FRAGMENT |
> > > > reclen);
> > > > +	return kernel_sendmsg(transport->sock, &msg, &iov, 1,
> > > > iov.iov_len);
> > > 
> > > So what does this do for performance? I'd expect that adding
> > > another
> > > dive into the socket layer will come with penalties.
> > 
> > NFSv3 on TCP, sec=sys, 56Gbs IBoIP, v4.20 + my v4.21 patches
> > fio, 8KB random, 70% read, 30% write, 16 threads, iodepth=16
> > 
> > Without this patch:
> > 
> >   read: IOPS=28.7k, BW=224MiB/s (235MB/s)(11.2GiB/51092msec)
> >  write: IOPS=12.3k, BW=96.3MiB/s (101MB/s)(4918MiB/51092msec)
> > 
> > With this patch:
> > 
> >   read: IOPS=28.6k, BW=224MiB/s (235MB/s)(11.2GiB/51276msec)
> >  write: IOPS=12.3k, BW=95.8MiB/s (100MB/s)(4914MiB/51276msec)
> > 
> > Seems like that's in the noise.
> 
> Sigh. That's because it was the same kernel. Again, with feeling:
> 
> 4.20.0-rc7-00048-g9274254:
>    read: IOPS=28.6k, BW=224MiB/s (235MB/s)(11.2GiB/51276msec)
>   write: IOPS=12.3k, BW=95.8MiB/s (100MB/s)(4914MiB/51276msec)
> 
> 4.20.0-rc7-00049-ga4dea15:
>    read: IOPS=27.2k, BW=212MiB/s (223MB/s)(11.2GiB/53979msec)
>   write: IOPS=11.7k, BW=91.1MiB/s (95.5MB/s)(4917MiB/53979msec)
> 

So about a 5% reduction in performance?

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com