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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: "Wang, Zhihong" <zhihong.wang@intel.com>,
	Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: "mst@redhat.com" <mst@redhat.com>, "dev@dpdk.org" <dev@dpdk.org>,
	"vkaplans@redhat.com" <vkaplans@redhat.com>
Subject: Re: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support to the TX path
Date: Fri, 28 Oct 2016 09:42:13 +0200	[thread overview]
Message-ID: <88169067-290d-a7bb-ab2c-c9b8ec1b1ded@redhat.com> (raw)
In-Reply-To: <8F6C2BD409508844A0EFC19955BE09414E7D90C7@SHSMSX103.ccr.corp.intel.com>



On 10/28/2016 02:49 AM, Wang, Zhihong wrote:
>
>> > -----Original Message-----
>> > From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
>> > Sent: Thursday, October 27, 2016 6:46 PM
>> > To: Maxime Coquelin <maxime.coquelin@redhat.com>
>> > Cc: Wang, Zhihong <zhihong.wang@intel.com>;
>> > stephen@networkplumber.org; Pierre Pfister (ppfister)
>> > <ppfister@cisco.com>; Xie, Huawei <huawei.xie@intel.com>; dev@dpdk.org;
>> > vkaplans@redhat.com; mst@redhat.com
>> > Subject: Re: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support
>> > to the TX path
>> >
>> > On Thu, Oct 27, 2016 at 12:35:11PM +0200, Maxime Coquelin wrote:
>>> > >
>>> > >
>>> > > On 10/27/2016 12:33 PM, Yuanhan Liu wrote:
>>>> > > >On Thu, Oct 27, 2016 at 11:10:34AM +0200, Maxime Coquelin wrote:
>>>>> > > >>Hi Zhihong,
>>>>> > > >>
>>>>> > > >>On 10/27/2016 11:00 AM, Wang, Zhihong wrote:
>>>>>> > > >>>Hi Maxime,
>>>>>> > > >>>
>>>>>> > > >>>Seems indirect desc feature is causing serious performance
>>>>>> > > >>>degradation on Haswell platform, about 20% drop for both
>>>>>> > > >>>mrg=on and mrg=off (--txqflags=0xf00, non-vector version),
>>>>>> > > >>>both iofwd and macfwd.
>>>>> > > >>I tested PVP (with macswap on guest) and Txonly/Rxonly on an Ivy
>> > Bridge
>>>>> > > >>platform, and didn't faced such a drop.
>>>> > > >
>>>> > > >I was actually wondering that may be the cause. I tested it with
>>>> > > >my IvyBridge server as well, I saw no drop.
>>>> > > >
>>>> > > >Maybe you should find a similar platform (Haswell) and have a try?
>>> > > Yes, that's why I asked Zhihong whether he could test Txonly in guest to
>>> > > see if issue is reproducible like this.
>> >
>> > I have no Haswell box, otherwise I could do a quick test for you. IIRC,
>> > he tried to disable the indirect_desc feature, then the performance
>> > recovered. So, it's likely the indirect_desc is the culprit here.
>> >
>>> > > I will be easier for me to find an Haswell machine if it has not to be
>>> > > connected back to back to and HW/SW packet generator.
> In fact simple loopback test will also do, without pktgen.
>
> Start testpmd in both host and guest, and do "start" in one
> and "start tx_first 32" in another.
>
> Perf drop is about 24% in my test.
>

Thanks, I never tried this test.
I managed to find an Haswell platform (Intel(R) Xeon(R) CPU E5-2699 v3
@ 2.30GHz), and can reproduce the problem with the loop test you
mention. I see a performance drop about 10% (8.94Mpps/8.08Mpps).
Out of curiosity, what are the numbers you get with your setup?

As I never tried this test, I run it again on my Sandy Bridge setup, and
I also see a performance regression, this time of 4%.

If I understand correctly the test, only 32 packets are allocated,
corresponding to a single burst, which is less than the queue size.
So it makes sense that the performance is lower with this test case.

Thanks,
Maxime

  reply	other threads:[~2016-10-28  7:42 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-23  8:28 [dpdk-dev] [PATCH v3] " Maxime Coquelin
2016-09-23 15:49 ` Michael S. Tsirkin
2016-09-23 18:02   ` Maxime Coquelin
2016-09-23 18:06     ` Michael S. Tsirkin
2016-09-23 18:16       ` Maxime Coquelin
2016-09-23 18:22         ` Michael S. Tsirkin
2016-09-23 20:24           ` Stephen Hemminger
2016-09-26  3:03             ` Yuanhan Liu
2016-09-26 12:25               ` Michael S. Tsirkin
2016-09-26 13:04                 ` Yuanhan Liu
2016-09-27  4:15 ` Yuanhan Liu
2016-09-27  7:25   ` Maxime Coquelin
2016-09-27  8:42 ` [dpdk-dev] [PATCH v4] " Maxime Coquelin
2016-09-27 12:18   ` Yuanhan Liu
2016-10-14  7:24   ` Wang, Zhihong
2016-10-14  7:34     ` Wang, Zhihong
2016-10-14 15:50     ` Maxime Coquelin
2016-10-17 11:23       ` Maxime Coquelin
2016-10-17 13:21         ` Yuanhan Liu
2016-10-17 14:14           ` Maxime Coquelin
2016-10-27  9:00             ` Wang, Zhihong
2016-10-27  9:10               ` Maxime Coquelin
2016-10-27  9:55                 ` Maxime Coquelin
2016-10-27 10:19                   ` Wang, Zhihong
2016-10-28  7:32                     ` Pierre Pfister (ppfister)
2016-10-28  7:58                       ` Maxime Coquelin
2016-11-01  8:15                         ` Yuanhan Liu
2016-11-01  9:39                           ` Thomas Monjalon
2016-11-02  2:44                             ` Yuanhan Liu
2016-10-27 10:33                 ` Yuanhan Liu
2016-10-27 10:35                   ` Maxime Coquelin
2016-10-27 10:46                     ` Yuanhan Liu
2016-10-28  0:49                       ` Wang, Zhihong
2016-10-28  7:42                         ` Maxime Coquelin [this message]
2016-10-31 10:01                           ` Wang, Zhihong
2016-11-02 10:51                             ` Maxime Coquelin
2016-11-03  8:11                               ` Maxime Coquelin
2016-11-04  6:18                                 ` Xu, Qian Q
2016-11-04  7:41                                   ` Maxime Coquelin
2016-11-04  7:20                                 ` Wang, Zhihong
2016-11-04  7:57                                   ` Maxime Coquelin
2016-11-04  7:59                                     ` Maxime Coquelin
2016-11-04 10:43                                       ` Wang, Zhihong
2016-11-04 11:22                                         ` Maxime Coquelin
2016-11-04 11:36                                           ` Yuanhan Liu
2016-11-04 11:39                                             ` Maxime Coquelin
2016-11-04 12:30                                           ` Wang, Zhihong
2016-11-04 12:54                                             ` Maxime Coquelin
2016-11-04 13:09                                               ` Wang, Zhihong
2016-11-08 10:51                                                 ` Wang, Zhihong
2016-10-27 10:53                   ` Maxime Coquelin
2016-10-28  6:05                     ` Xu, Qian Q

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