From: "lihuisong (C)" <lihuisong@huawei.com>
To: "Morten Brørup" <mb@smartsharesystems.com>,
"Ferruh Yigit" <ferruh.yigit@amd.com>,
"Stephen Hemminger" <stephen@networkplumber.org>
Cc: <dev@dpdk.org>, <thomas@monjalon.net>,
<andrew.rybchenko@oktetlabs.ru>, <liuyonglong@huawei.com>
Subject: Re: [PATCH v3 0/3] introduce maximum Rx buffer size
Date: Fri, 3 Nov 2023 10:13:10 +0800 [thread overview]
Message-ID: <148fd6ac-9e03-da01-dcf7-bf95d37088c4@huawei.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35E9EFCB@smartserver.smartshare.dk>
在 2023/11/3 0:51, Morten Brørup 写道:
>> From: Ferruh Yigit [mailto:ferruh.yigit@amd.com]
>> Sent: Thursday, 2 November 2023 17.24
>>
>> On 11/2/2023 1:59 AM, lihuisong (C) wrote:
>>> 在 2023/11/2 0:08, Stephen Hemminger 写道:
>>>> On Wed, 1 Nov 2023 10:36:07 +0800
>>>> "lihuisong (C)" <lihuisong@huawei.com> wrote:
>>>>
>>>>>> Do we need to report this size? It's a common feature for all
>> PMDs.
>>>>>> It would make sense then to have max_rx_bufsize set to 16K by
>> default
>>>>>> in ethdev, and PMD could then raise/lower based on hardware.
>>>>> It is not appropriate to set to 16K by default in ethdev layer.
>>>>> Because I don't see any check for the upper bound in some driver,
>> like
>>>>> axgbe, enetc and so on.
>>>>> I'm not sure if they have no upper bound.
>>>>> And some driver's maximum buffer size is "16384(16K) - 128"
>>>>> So it's better to set to UINT32_MAX by default.
>>>>> what do you think?
>>>> The goal is always giving application a working upper bound, and
>>>> enforcing
>>>> that as much as possible in ethdev layer. It doesnt matter which
>> pattern
>>>> does that. Fortunately, telling application an incorrect answer is
>>>> not fatal.
>>>> If over estimated, application pool would be wasting space.
>>>> If under estimated, application will get more fragmented packets.
>>> I know what you mean.
>>> If we set UINT32_MAX, it just means that driver don't report this
>> upper
>>> bound.
>>> This is also a very common way of handling. And it has no effect on
>> the
>>> drivers that doesn't report this value.
>>> On the contrary, if we set a default value (like 16K) in ethdev, user
>>> may be misunderstood and confused by that, right?
>>> After all, this isn't the real upper bound of all drivers. And this
>>> fixed default value may affect the behavior of some driver that I
>> didn't
>>> find their upper bound.
>>> So I'd like to keep it as UINT32_MAX.
>>>
>>
>> Hi Stephen, Morten,
>>
>> I saw scattered Rx mentioned, there may be some misalignment,
>> the purpose of the patch is not to enable application to set as big as
>> possible mbuf size, so that application can escape from parsing
>> multi-segment mbufs.
>> Indeed application can provide a large mbuf anyway, to have same
>> result,
>> without knowing this information.
>>
>> Main motivation is other way around, device may have restriction on
>> buffer size that a single descriptor can address, independent from
>> scattered Rx used, if mbuf size is bigger than this device limit, each
>> mbuf will have some unused space.
>> Patch has intention to inform this max per mbuf/descriptor buffer size,
>> so that application doesn't allocate bigger mbuf and waste memory.
> Good point!
+1
>
> Let's categorize this patch series as a memory optimization for applications that support jumbo frames, but are trying to avoid (or reduce) scattered RX. :-)
User can select to receive jumbo frames in one mbuf or descriptor rather
then multi-mbuf even if no this patch.
In other words, using big Rx buffer size is just a way to receive jumbo
frames.
>
next prev parent reply other threads:[~2023-11-03 2:13 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-08 4:02 [RFC] ethdev: " Huisong Li
2023-08-11 12:07 ` Andrew Rybchenko
2023-08-15 8:16 ` lihuisong (C)
2023-08-15 11:10 ` [PATCH v1 0/3] " Huisong Li
2023-08-15 11:10 ` [PATCH v1 1/3] ethdev: " Huisong Li
2023-09-28 15:56 ` Ferruh Yigit
2023-10-24 12:21 ` lihuisong (C)
2023-08-15 11:10 ` [PATCH v1 2/3] app/testpmd: add maximum Rx buffer size display Huisong Li
2023-08-15 11:10 ` [PATCH v1 3/3] net/hns3: report maximum buffer size Huisong Li
2023-10-27 4:15 ` [PATCH v2 0/3] introduce maximum Rx " Huisong Li
2023-10-27 4:15 ` [PATCH v2 1/3] ethdev: " Huisong Li
2023-10-27 6:27 ` fengchengwen
2023-10-27 7:40 ` Morten Brørup
2023-10-28 1:23 ` lihuisong (C)
2023-10-27 4:15 ` [PATCH v2 2/3] app/testpmd: add maximum Rx buffer size display Huisong Li
2023-10-27 6:28 ` fengchengwen
2023-10-27 4:15 ` [PATCH v2 3/3] net/hns3: report maximum buffer size Huisong Li
2023-10-27 6:17 ` fengchengwen
2023-10-28 1:48 ` [PATCH v3 0/3] introduce maximum Rx " Huisong Li
2023-10-28 1:48 ` [PATCH v3 1/3] ethdev: " Huisong Li
2023-10-29 15:43 ` Stephen Hemminger
2023-10-30 3:08 ` lihuisong (C)
2023-10-28 1:48 ` [PATCH v3 2/3] app/testpmd: add maximum Rx buffer size display Huisong Li
2023-10-28 1:48 ` [PATCH v3 3/3] net/hns3: report maximum buffer size Huisong Li
2023-10-29 15:48 ` [PATCH v3 0/3] introduce maximum Rx " Stephen Hemminger
2023-10-30 1:25 ` lihuisong (C)
2023-10-30 18:48 ` Stephen Hemminger
2023-10-31 2:57 ` lihuisong (C)
2023-10-31 7:48 ` Morten Brørup
2023-10-31 15:40 ` Stephen Hemminger
2023-11-01 2:36 ` lihuisong (C)
2023-11-01 16:08 ` Stephen Hemminger
2023-11-02 1:59 ` lihuisong (C)
2023-11-02 16:23 ` Ferruh Yigit
2023-11-02 16:51 ` Morten Brørup
2023-11-02 17:05 ` Ferruh Yigit
2023-11-02 17:12 ` Morten Brørup
2023-11-02 17:35 ` Ferruh Yigit
2023-11-03 2:13 ` lihuisong (C) [this message]
2023-11-02 12:16 ` [PATCH v4 " Huisong Li
2023-11-02 12:16 ` [PATCH v4 1/3] ethdev: " Huisong Li
2023-11-02 16:35 ` Ferruh Yigit
2023-11-03 2:21 ` lihuisong (C)
2023-11-03 3:30 ` Ferruh Yigit
2023-11-03 6:27 ` lihuisong (C)
2023-11-02 12:16 ` [PATCH v4 2/3] app/testpmd: add maximum Rx buffer size display Huisong Li
2023-11-02 16:42 ` Ferruh Yigit
2023-11-03 2:39 ` lihuisong (C)
2023-11-03 3:53 ` Ferruh Yigit
2023-11-03 6:37 ` lihuisong (C)
2023-11-02 12:16 ` [PATCH v4 3/3] net/hns3: report maximum buffer size Huisong Li
2023-11-03 10:27 ` [PATCH v5 0/3] introduce maximum Rx " Huisong Li
2023-11-03 10:27 ` [PATCH v5 1/3] ethdev: " Huisong Li
2023-11-03 12:37 ` Ivan Malov
2023-11-03 10:27 ` [PATCH v5 2/3] app/testpmd: add maximum Rx buffer size display Huisong Li
2023-11-03 10:27 ` [PATCH v5 3/3] net/hns3: report maximum buffer size Huisong Li
2023-11-03 11:53 ` [PATCH v5 0/3] introduce maximum Rx " Ferruh Yigit
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