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Subject: Re: [PATCH] SUNRPC: Remove rpc_xprt::tsh_size
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <076cce85045dbaab3ca40947b2599f96cff66b53.camel@hammerspace.com>
Date:   Thu, 3 Jan 2019 16:35:00 -0500
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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Message-Id: <1353EAC5-5BEE-461E-A11E-31F00FC7B946@oracle.com>
References: <20190103182649.4148.19838.stgit@manet.1015granger.net>
 <0331de80b8161f8bf16a92de20049cafb0c228da.camel@hammerspace.com>
 <90B38E07-3241-4CCD-A4C8-AB78BADFB0CD@oracle.com>
 <791EE189-59E5-4D58-9CF6-6D2CFC6C1210@oracle.com>
 <076cce85045dbaab3ca40947b2599f96cff66b53.camel@hammerspace.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk


> On Jan 3, 2019, at 4:28 PM, Trond Myklebust <trondmy@hammerspace.com> =
wrote:
>=20
> 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:
>>>=20
>>>> On Jan 3, 2019, at 1:47 PM, Trond Myklebust <
>>>> trondmy@hammerspace.com> wrote:
>>>>=20
>>>> On Thu, 2019-01-03 at 13:29 -0500, Chuck Lever wrote:
>>>>> +	reclen =3D req->rq_snd_buf.len;
>>>>> +	marker =3D cpu_to_be32(RPC_LAST_STREAM_FRAGMENT |
>>>>> reclen);
>>>>> +	return kernel_sendmsg(transport->sock, &msg, &iov, 1,
>>>>> iov.iov_len);
>>>>=20
>>>> So what does this do for performance? I'd expect that adding
>>>> another
>>>> dive into the socket layer will come with penalties.
>>>=20
>>> NFSv3 on TCP, sec=3Dsys, 56Gbs IBoIP, v4.20 + my v4.21 patches
>>> fio, 8KB random, 70% read, 30% write, 16 threads, iodepth=3D16
>>>=20
>>> Without this patch:
>>>=20
>>>  read: IOPS=3D28.7k, BW=3D224MiB/s (235MB/s)(11.2GiB/51092msec)
>>> write: IOPS=3D12.3k, BW=3D96.3MiB/s (101MB/s)(4918MiB/51092msec)
>>>=20
>>> With this patch:
>>>=20
>>>  read: IOPS=3D28.6k, BW=3D224MiB/s (235MB/s)(11.2GiB/51276msec)
>>> write: IOPS=3D12.3k, BW=3D95.8MiB/s (100MB/s)(4914MiB/51276msec)
>>>=20
>>> Seems like that's in the noise.
>>=20
>> Sigh. That's because it was the same kernel. Again, with feeling:
>>=20
>> 4.20.0-rc7-00048-g9274254:
>>   read: IOPS=3D28.6k, BW=3D224MiB/s (235MB/s)(11.2GiB/51276msec)
>>  write: IOPS=3D12.3k, BW=3D95.8MiB/s (100MB/s)(4914MiB/51276msec)
>>=20
>> 4.20.0-rc7-00049-ga4dea15:
>>   read: IOPS=3D27.2k, BW=3D212MiB/s (223MB/s)(11.2GiB/53979msec)
>>  write: IOPS=3D11.7k, BW=3D91.1MiB/s (95.5MB/s)(4917MiB/53979msec)
>>=20
>=20
> 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.


--
Chuck Lever