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

[Chuck Lever <chuck.lever@oracle.com>]

> On Jan 3, 2019, at 4:35 PM, Chuck Lever <chuck.lever@oracle.com> wrote:
> 
>> On Jan 3, 2019, at 4:28 PM, Trond Myklebust <trondmy@hammerspace.com> wrote:
>> 
>> 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?
> 
> On this workload, yes.
> 
> Could send the record marker in xs_send_kvec with the head[0] iovec.
> I'm going to try that next.

That helps:

Linux 4.20.0-rc7-00049-g664f679 #651 SMP Thu Jan 3 17:35:26 EST 2019

   read: IOPS=28.7k, BW=224MiB/s (235MB/s)(11.2GiB/51185msec)
  write: IOPS=12.3k, BW=96.1MiB/s (101MB/s)(4919MiB/51185msec)

--
Chuck Lever