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From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Avi Kivity <avi@cloudius-systems.com>,
	"didier.pallard" <didier.pallard@6wind.com>,
	Vlad Zolotarov <vladz@cloudius-systems.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1 for all NICs but 82598
Date: Fri, 11 Sep 2015 07:55:08 -0700 (PDT)	[thread overview]
Message-ID: <1762144.1LKiyImgC1@xps13> (raw)
In-Reply-To: <55F2E997.5050009@cloudius-systems.com>

2015-09-11 17:47, Avi Kivity:
> On 09/11/2015 05:25 PM, didier.pallard wrote:
> > On 08/25/2015 08:52 PM, Vlad Zolotarov wrote:
> >>
> >> Helin, the issue has been seen on x540 devices. Pls., see a chapter 
> >> 7.2.1.1 of x540 devices spec:
> >>
> >> A packet (or multiple packets in transmit segmentation) can span any 
> >> number of
> >> buffers (and their descriptors) up to a limit of 40 minus WTHRESH 
> >> minus 2 (see
> >> Section 7.2.3.3 for Tx Ring details and section Section 7.2.3.5.1 for 
> >> WTHRESH
> >> details). For best performance it is recommended to minimize the 
> >> number of buffers
> >> as possible.
> >>
> >> Could u, pls., clarify why do u think that the maximum number of data 
> >> buffers is limited by 8?
> >>
> >> thanks,
> >> vlad
> >
> > Hi vlad,
> >
> > Documentation states that a packet (or multiple packets in transmit 
> > segmentation) can span any number of
> > buffers (and their descriptors) up to a limit of 40 minus WTHRESH 
> > minus 2.
> >
> > Shouldn't there be a test in transmit function that drops properly the 
> > mbufs with a too large number of
> > segments, while incrementing a statistic; otherwise transmit function 
> > may be locked by the faulty packet without
> > notification.
> >
> 
> What we proposed is that the pmd expose to dpdk, and dpdk expose to the 
> application, an mbuf check function.  This way applications that can 
> generate complex packets can verify that the device will be able to 
> process them, and applications that only generate simple mbufs can avoid 
> the overhead by not calling the function.

More than a check, it should be exposed as a capability of the port.
Anyway, if the application sends too much segments, the driver must
drop it to avoid hang, and maintain a dedicated statistic counter to allow
easy debugging.

  reply	other threads:[~2015-09-11 14:55 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-08-13 18:06 Vlad Zolotarov
2015-08-13 20:28 ` Zhang, Helin
2015-08-14  5:37   ` Vlad Zolotarov
2015-08-19  0:42     ` Lu, Wenzhuo
2015-08-19  4:55       ` Vladislav Zolotarov
2015-08-19  7:43         ` Ananyev, Konstantin
2015-08-19 10:02           ` Vlad Zolotarov
2015-08-20  8:41             ` Ananyev, Konstantin
2015-08-20  8:56               ` Vlad Zolotarov
2015-08-20  9:05                 ` Vlad Zolotarov
2015-08-20  9:06                   ` Vlad Zolotarov
2015-08-25 17:33                     ` Ananyev, Konstantin
2015-08-25 17:39                       ` Avi Kivity
2015-08-19 17:29         ` Zhang, Helin
2015-08-25 18:13           ` Zhang, Helin
2015-08-25 18:33             ` Vladislav Zolotarov
2015-08-25 18:43               ` Zhang, Helin
2015-08-25 18:52                 ` Vlad Zolotarov
2015-08-25 19:16                   ` Zhang, Helin
2015-08-25 19:23                     ` Avi Kivity
2015-08-25 19:30                     ` Vladislav Zolotarov
2015-08-25 20:07                       ` Vlad Zolotarov
2015-08-25 20:13                       ` Zhang, Helin
2015-09-09 12:18                         ` Thomas Monjalon
2015-09-09 13:19                           ` Ananyev, Konstantin
2015-09-11 15:17                             ` Vladislav Zolotarov
2015-09-11 14:25                   ` didier.pallard
2015-09-11 14:47                     ` Avi Kivity
2015-09-11 14:55                       ` Thomas Monjalon [this message]
2015-09-11 15:12                         ` Vladislav Zolotarov
2015-09-11 15:43                           ` Avi Kivity
2015-09-11 16:04                             ` Vladislav Zolotarov
2015-09-11 16:07                               ` Richardson, Bruce
2015-09-11 16:14                                 ` Vladislav Zolotarov
2015-09-11 17:44                                 ` Avi Kivity
2015-09-11 16:08                             ` Thomas Monjalon
2015-09-11 16:18                               ` Vladislav Zolotarov
2015-09-11 17:17                                 ` Matthew Hall
2015-09-11 17:42                                   ` Ananyev, Konstantin
2015-09-11 17:58                                     ` Matthew Hall
2015-09-11 17:48                               ` Avi Kivity
2015-09-13 11:47                                 ` Ananyev, Konstantin
2015-09-13 12:24                                   ` Vlad Zolotarov
2015-09-13 12:32                                   ` Avi Kivity
2015-09-13 15:54                                     ` Ananyev, Konstantin
2015-09-13 16:01                                       ` Avi Kivity
2015-09-11 16:00                           ` Richardson, Bruce
2015-09-11 16:13                             ` Vladislav Zolotarov

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