From: Mihai Brodschi <mihai.brodschi@broadcom.com>
To: Ferruh Yigit <ferruh.yigit@amd.com>, Jakub Grajciar <jgrajcia@cisco.com>
Cc: dev@dpdk.org, stable@dpdk.org,
Mihai Brodschi <mihai.brodschi@broadcom.com>
Subject: Re: [PATCH v2] net/memif: fix buffer overflow in zero copy Rx
Date: Sat, 31 Aug 2024 16:38:20 +0300 [thread overview]
Message-ID: <39430e7d-161e-40c3-bbb0-a7cd5de0b7cf@broadcom.com> (raw)
In-Reply-To: <e335a5c7-2b4f-46a5-b907-64cd3fdeca13@amd.com>
Hi Ferruh,
Apologies for the late response.
I've run some performance tests for the two proposed solutions.
In the tables below, the rte_memcpy results correspond to this patch.
The 2xpktmbuf_alloc results correspond to the other proposed solution.
bash commands:
server# ./dpdk-testpmd --vdev=net_memif0,id=1,role=server,bsize=1024,rsize=8 --single -l<SERVER_CORES> --file=test1 -- --nb-cores <NB_CORES> --txq <NB_CORES> --rxq <NB_CORES> --burst <BURST> -i
client# ./dpdk-testpmd --vdev=net_memif0,id=1,role=client,bsize=1024,rsize=8,zero-copy=yes --single -l<CLIENT_CORES> --file=test2 -- --nb-cores <NB_CORES> --txq <NB_CORES> --rxq <NB_CORES> --burst <BURST> -i
testpmd commands:
client:
testpmd> start
server:
testpmd> start tx_first
CPU: AMD EPYC 7713P
RAM: DDR4-3200
OS: Debian 12
DPDK: 22.11.1
SERVER_CORES=72,8,9,10,11
CLIENT_CORES=76,12,13,14,15
Results:
==================================================================
| | 1 CORE | 2 CORES | 4 CORES |
==================================================================
| unpatched burst=32 | 9.95 Gbps | 19.24 Gbps | 36.4 Gbps |
------------------------------------------------------------------
| 2xpktmbuf_alloc burst=32 | 9.86 Gbps | 18.88 Gbps | 36.6 Gbps |
------------------------------------------------------------------
| 2xpktmbuf_alloc burst=31 | 9.17 Gbps | 18.69 Gbps | 35.1 Gbps |
------------------------------------------------------------------
| rte_memcpy burst=32 | 9.54 Gbps | 19.10 Gbps | 36.6 Gbps |
------------------------------------------------------------------
| rte_memcpy burst=31 | 9.39 Gbps | 18.53 Gbps | 35.5 Gbps |
==================================================================
CPU: Intel Core i7-14700HX
RAM: DDR5-5600
OS: Ubuntu 24.04.1
DPDK: 23.11.1
SERVER_CORES=0,1,3,5,7
CLIENT_CORES=8,9,11,13,15
Results:
==================================================================
| | 1 CORE | 2 CORES | 4 CORES |
==================================================================
| unpatched burst=32 | 15.52 Gbps | 27.35 Gbps | 46.8 Gbps |
------------------------------------------------------------------
| 2xpktmbuf_alloc burst=32 | 15.49 Gbps | 27.68 Gbps | 46.4 Gbps |
------------------------------------------------------------------
| 2xpktmbuf_alloc burst=31 | 14.98 Gbps | 26.75 Gbps | 45.2 Gbps |
------------------------------------------------------------------
| rte_memcpy burst=32 | 15.99 Gbps | 28.44 Gbps | 49.3 Gbps |
------------------------------------------------------------------
| rte_memcpy burst=31 | 14.85 Gbps | 27.32 Gbps | 46.3 Gbps |
==================================================================
On 19/07/2024 12:03, Ferruh Yigit wrote:
> On 7/8/2024 12:45 PM, Ferruh Yigit wrote:
>> On 7/8/2024 4:39 AM, Mihai Brodschi wrote:
>>>
>>>
>>> On 07/07/2024 21:46, Mihai Brodschi wrote:
>>>>
>>>>
>>>> On 07/07/2024 18:18, Mihai Brodschi wrote:
>>>>>
>>>>>
>>>>> On 07/07/2024 17:05, Ferruh Yigit wrote:
>>>>>>
>>>>>> My expectation is numbers should be like following:
>>>>>>
>>>>>> Initially:
>>>>>> size = 256
>>>>>> head = 0
>>>>>> tail = 0
>>>>>>
>>>>>> In first refill:
>>>>>> n_slots = 256
>>>>>> head = 256
>>>>>> tail = 0
>>>>>>
>>>>>> Subsequent run that 32 slots used:
>>>>>> head = 256
>>>>>> tail = 32
>>>>>> n_slots = 32
>>>>>> rte_pktmbuf_alloc_bulk(mq, buf[head & mask], n_slots);
>>>>>> head & mask = 0
>>>>>> // So it fills first 32 elements of buffer, which is inbound
>>>>>>
>>>>>> This will continue as above, combination of only gap filled and head
>>>>>> masked with 'mask' provides the wrapping required.
>>>>>
>>>>> If I understand correctly, this works only if eth_memif_rx_zc always processes
>>>>> a number of packets which is a power of 2, so that the ring's head always wraps
>>>>> around at the end of a refill loop, never in the middle of it.
>>>>> Is there any reason this should be the case?
>>>>> Maybe the tests don't trigger the crash because this condition holds true for them?
>>>>
>>>> Here's how to reproduce the crash on DPDK stable 23.11.1, using testpmd:
>>>>
>>>> Server:
>>>> # ./dpdk-testpmd --vdev=net_memif0,id=1,role=server,bsize=1024,rsize=8 --single-file-segments -l2,3 --file-prefix test1 -- -i
>>>>
>>>> Client:
>>>> # ./dpdk-testpmd --vdev=net_memif0,id=1,role=client,bsize=1024,rsize=8,zero-copy=yes --single-file-segments -l4,5 --file-prefix test2 -- -i
>>>> testpmd> start
>>>>
>>>> Server:
>>>> testpmd> start tx_first
>>>> testpmt> set burst 15
>>>>
>>>> At this point, the client crashes with a segmentation fault.
>>>> Before the burst is set to 15, its default value is 32.
>>>> If the receiver processes packets in bursts of size 2^N, the crash does not occur.
>>>> Setting the burst size to any power of 2 works, anything else crashes.
>>>> After applying this patch, the crashes are completely gone.
>>>
>>> Sorry, this might not crash with a segmentation fault. To confirm the mempool is
>>> corrupted, please compile DPDK with debug=true and the c_args -DRTE_LIBRTE_MEMPOOL_DEBUG.
>>> You should see the client panic when changing the burst size to not be a power of 2.
>>> This also works on the latest main branch.
>>>
>>
>> Hi Mihai,
>>
>> Right, if the buffer size is not multiple of burst size, issue is valid.
>> And as there is a requirement to have buffer size power of two, burst
>> should have the same.
>> I assume this issue is not caught before because default burst size is 32.
>>
>> Can you please share some performance impact of the change, with two
>> possible solutions we discussed above?
>>
>> Other option is to add this as a limitation to the memif zero copy, but
>> this won't be good for usability.
>>
>> We can decide based on performance numbers.
>>
>>
>
> Hi Jakup,
>
> Do you have any comment on this?
>
> I think we should either document this as limitation of the driver, or
> fix it, and if so need to decide the fix.
>
--
This electronic communication and the information and any files transmitted
with it, or attached to it, are confidential and are intended solely for
the use of the individual or entity to whom it is addressed and may contain
information that is confidential, legally privileged, protected by privacy
laws, or otherwise restricted from disclosure to anyone else. If you are
not the intended recipient or the person responsible for delivering the
e-mail to the intended recipient, you are hereby notified that any use,
copying, distributing, dissemination, forwarding, printing, or copying of
this e-mail is strictly prohibited. If you received this e-mail in error,
please return the e-mail to the sender, delete it from your computer, and
destroy any printed copy of it.
next prev parent reply other threads:[~2024-08-31 13:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-28 21:01 Mihai Brodschi
2024-07-01 4:57 ` Patrick Robb
2024-07-07 2:12 ` Ferruh Yigit
2024-07-07 5:50 ` Mihai Brodschi
2024-07-07 14:05 ` Ferruh Yigit
2024-07-07 15:18 ` Mihai Brodschi
2024-07-07 18:46 ` Mihai Brodschi
2024-07-08 3:39 ` Mihai Brodschi
2024-07-08 11:45 ` Ferruh Yigit
2024-07-19 9:03 ` Ferruh Yigit
2024-08-31 13:38 ` Mihai Brodschi [this message]
2024-10-10 2:00 ` Ferruh Yigit
2024-10-10 2:33 ` Ferruh Yigit
2024-07-07 5:31 Mihai Brodschi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=39430e7d-161e-40c3-bbb0-a7cd5de0b7cf@broadcom.com \
--to=mihai.brodschi@broadcom.com \
--cc=dev@dpdk.org \
--cc=ferruh.yigit@amd.com \
--cc=jgrajcia@cisco.com \
--cc=stable@dpdk.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).