From: fengchengwen <fengchengwen@huawei.com>
To: "Ma, WenwuX" <wenwux.ma@intel.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: "Jiale, SongX" <songx.jiale@intel.com>,
"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [PATCH v2] dmadev: fix structure alignment
Date: Fri, 15 Mar 2024 16:31:53 +0800 [thread overview]
Message-ID: <efb36dd7-87e7-3fcb-9ae0-067d16f13676@huawei.com> (raw)
In-Reply-To: <MN0PR11MB6110BEA17043820568CD9BC4EB282@MN0PR11MB6110.namprd11.prod.outlook.com>
Hi Wenwu,
On 2024/3/15 15:44, Ma, WenwuX wrote:
> Hi Chengwen,
>
>> -----Original Message-----
>> From: Ma, WenwuX
>> Sent: Friday, March 15, 2024 2:26 PM
>> To: fengchengwen <fengchengwen@huawei.com>; dev@dpdk.org
>> Cc: Jiale, SongX <songx.jiale@intel.com>; stable@dpdk.org
>> Subject: RE: [PATCH v2] dmadev: fix structure alignment
>>
>> Hi Chengwen,
>>
>>> -----Original Message-----
>>> From: fengchengwen <fengchengwen@huawei.com>
>>> Sent: Friday, March 15, 2024 2:06 PM
>>> To: Ma, WenwuX <wenwux.ma@intel.com>; dev@dpdk.org
>>> Cc: Jiale, SongX <songx.jiale@intel.com>; stable@dpdk.org
>>> Subject: Re: [PATCH v2] dmadev: fix structure alignment
>>>
>>> Hi Wenwu,
>>>
>>> On 2024/3/15 9:43, Wenwu Ma wrote:
>>>> The structure rte_dma_dev needs only 8 byte alignment.
>>>> This patch replaces __rte_cache_aligned of rte_dma_dev with
>>>> __rte_aligned(8).
>>>>
>>>> Fixes: b36970f2e13e ("dmadev: introduce DMA device library")
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Wenwu Ma <wenwux.ma@intel.com>
>>>> ---
>>>> v2:
>>>> - Because of performance drop, adjust the code to
>>>> no longer demand cache line alignment
>>>
>>> Which two versions observed performance drop? And which benchmark
>>> observed drop?
>>> Could you provide more information?
>>>
>>>>
>> V1 patch:
>> https://patches.dpdk.org/project/dpdk/patch/20240308053711.1260154-
>> 1-wenwux.ma@intel.com/
>>
>> To view detailed results, visit:
>> https://lab.dpdk.org/results/dashboard/patchsets/29472/
>>
>>>> ---
>>>> lib/dmadev/rte_dmadev_pmd.h | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/lib/dmadev/rte_dmadev_pmd.h
>>> b/lib/dmadev/rte_dmadev_pmd.h
>>>> index 58729088ff..b569bb3502 100644
>>>> --- a/lib/dmadev/rte_dmadev_pmd.h
>>>> +++ b/lib/dmadev/rte_dmadev_pmd.h
>>>> @@ -122,7 +122,7 @@ enum rte_dma_dev_state {
>>>> * @internal
>>>> * The generic data structure associated with each DMA device.
>>>> */
>>>> -struct __rte_cache_aligned rte_dma_dev {
>>>> +struct __rte_aligned(8) rte_dma_dev {
>>>
>>> The DMA fast-path was implemented by struct rte_dma_fp_objs, which is
>>> not rte_dma_dev? So why is it a problem here?
>>>
>>> Thanks
>>>
>> The DMA device object is expected to align cache line, so clang will use
>> “vmovaps” assembly instruction,
>>
>> And the instruction demands 16 bytes alignment or will cause segment fault in
>> some environments.
>>
> Test case:
> 1. compile dpdk
> rm -rf x86_64-native-linuxapp-clang
> CC=clang meson -Denable_kmods=True -Dlibdir=lib --default-library=static x86_64-native-linuxapp-clang
> ninja -C x86_64-native-linuxapp-clang -j 72
> 2. start dpdk-test
> /root/dpdk/x86_64-native-linuxapp-clang/app/dpdk-test -l 0-39 --vdev=dma_skeleton -a 31:00.0 -a 31:00.1 -a 31:00.2 -a 31:00.3 (Note: If it cannot be reproduced, please try using a different core)
> 3. exit dpdk-test
> RTE>>quit
> Segmentation fault (core dumped)
I will try to reproduce, but still a question: does above test has already merged your patch [1] or the current main branch code has this problem?
[1] https://patches.dpdk.org/project/dpdk/patch/20240308053711.1260154-1-wenwux.ma@intel.com/
Thanks
>
>>
>>>> /** Device info which supplied during device initialization. */
>>>> struct rte_device *device;
>>>> struct rte_dma_dev_data *data; /**< Pointer to shared device data.
>>>> */
>>>>
next prev parent reply other threads:[~2024-03-15 8:32 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-08 5:37 [PATCH] " Wenwu Ma
2024-03-08 7:01 ` fengchengwen
2024-03-15 1:43 ` [PATCH v2] " Wenwu Ma
2024-03-15 6:02 ` Tyler Retzlaff
2024-03-15 6:06 ` fengchengwen
2024-03-15 6:25 ` Ma, WenwuX
2024-03-15 7:44 ` Ma, WenwuX
2024-03-15 8:31 ` fengchengwen [this message]
2024-03-15 9:27 ` Ma, WenwuX
2024-03-20 4:11 ` fengchengwen
2024-03-20 7:34 ` Ma, WenwuX
2024-03-19 9:48 ` Jiale, SongX
2024-03-20 7:23 ` [PATCH v3] " Wenwu Ma
2024-03-20 9:31 ` fengchengwen
2024-06-27 12:46 ` Thomas Monjalon
2024-03-20 11:37 ` Thomas Monjalon
2024-03-21 1:25 ` Ma, WenwuX
2024-03-21 8:30 ` Thomas Monjalon
2024-03-21 8:57 ` Ma, WenwuX
2024-03-21 9:18 ` Ma, WenwuX
2024-03-21 10:06 ` Thomas Monjalon
2024-03-21 16:05 ` Tyler Retzlaff
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