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From: Feifei Wang <Feifei.Wang2@arm.com>
To: Slava Ovsiienko <viacheslavo@nvidia.com>,
	Matan Azrad <matan@nvidia.com>,
	 Shahaf Shuler <shahafs@nvidia.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, nd <nd@arm.com>,
	Ruifeng Wang <Ruifeng.Wang@arm.com>, nd <nd@arm.com>
Subject: [dpdk-dev] 回复: [PATCH v3 2/2] net/mlx5: remove unnecessary wmb for Memory Region cache
Date: Wed, 19 May 2021 01:54:42 +0000
Message-ID: <DB9PR08MB6923D8A116844918B541F408C82B9@DB9PR08MB6923.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <DM6PR12MB3753D9DC429E4C1F87459E7CDF2C9@DM6PR12MB3753.namprd12.prod.outlook.com>

Also thanks for your patient communication and explanation.
A wonderful discussion~

Best Regards
Feifei
> -----邮件原件-----
> 发件人: Slava Ovsiienko <viacheslavo@nvidia.com>
> 发送时间: 2021年5月18日 18:18
> 收件人: Feifei Wang <Feifei.Wang2@arm.com>; Matan Azrad
> <matan@nvidia.com>; Shahaf Shuler <shahafs@nvidia.com>
> 抄送: dev@dpdk.org; nd <nd@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>
> 主题: RE: [PATCH v3 2/2] net/mlx5: remove unnecessary wmb for Memory
> Region cache
> 
> > -----Original Message-----
> > From: Feifei Wang <feifei.wang2@arm.com>
> > Sent: Tuesday, May 18, 2021 11:51
> > To: Matan Azrad <matan@nvidia.com>; Shahaf Shuler
> > <shahafs@nvidia.com>; Slava Ovsiienko <viacheslavo@nvidia.com>
> > Cc: dev@dpdk.org; nd@arm.com; Feifei Wang <feifei.wang2@arm.com>;
> > Ruifeng Wang <ruifeng.wang@arm.com>
> > Subject: [PATCH v3 2/2] net/mlx5: remove unnecessary wmb for Memory
> > Region cache
> >
> > 'dev_gen' is a variable to trigger all cores to flush their local
> > caches once the global MR cache has been rebuilt.
> >
> > This is due to MR cache's R/W lock can maintain synchronization
> > between
> > threads:
> >
> > 1. dev_gen and global cache updating ordering inside the lock
> > protected section does not matter. Because other threads cannot take
> > the lock until global cache has been updated. Thus, in out of order
> > platform, even if other agents firstly observe updated dev_gen but
> > global does not update, they also have to wait the lock. As a result,
> > it is unnecessary to add a wmb between global cache rebuilding and
> > updating the dev_gen to keep the memory store order.
> >
> > 2. Store-Release of unlock provides the implicit wmb at the level
> > visible by software. This makes 'rebuilding global cache' and
> > 'updating dev_gen' be observed before local_cache starts to be updated
> > by other agents. Thus, wmb after 'updating dev_gen' can be removed.
> >
> > Suggested-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
> 
> Thanks a lot for patience and cooperation.
> With best regards,
> Slava

  reply	other threads:[~2021-05-19  1:54 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-18  7:18 [dpdk-dev] [PATCH v1 0/4] refactor SMP barriers for net/mlx Feifei Wang
2021-03-18  7:18 ` [dpdk-dev] [PATCH v1 1/4] net/mlx4: fix rebuild bug for Memory Region cache Feifei Wang
2021-03-18  7:18 ` [dpdk-dev] [PATCH v1 2/4] net/mlx4: replace SMP barrier with C11 barriers Feifei Wang
2021-03-18  7:18 ` [dpdk-dev] [PATCH v1 3/4] net/mlx5: fix rebuild bug for Memory Region cache Feifei Wang
2021-04-12  8:27   ` Slava Ovsiienko
2021-04-13  5:20     ` [dpdk-dev] 回复: " Feifei Wang
2021-04-19 18:50       ` [dpdk-dev] " Slava Ovsiienko
2021-04-20  5:53         ` [dpdk-dev] 回复: " Feifei Wang
2021-04-20  7:29           ` Feifei Wang
2021-04-20  7:53             ` [dpdk-dev] " Slava Ovsiienko
2021-04-20  8:42               ` [dpdk-dev] 回复: " Feifei Wang
2021-05-06  2:52                 ` Feifei Wang
2021-05-06 11:21                   ` [dpdk-dev] " Slava Ovsiienko
2021-05-07  6:36                     ` [dpdk-dev] 回复: " Feifei Wang
2021-05-07 10:14                       ` [dpdk-dev] " Slava Ovsiienko
2021-05-08  3:13                         ` [dpdk-dev] 回复: " Feifei Wang
2021-05-11  8:18                           ` [dpdk-dev] " Slava Ovsiienko
2021-05-12  5:34                             ` [dpdk-dev] 回复: " Feifei Wang
2021-05-12 11:07                               ` [dpdk-dev] " Slava Ovsiienko
2021-05-13  5:49                                 ` [dpdk-dev] 回复: " Feifei Wang
2021-05-13 10:49                                   ` [dpdk-dev] " Slava Ovsiienko
2021-05-14  5:18                                     ` [dpdk-dev] 回复: " Feifei Wang
2021-03-18  7:18 ` [dpdk-dev] [PATCH v1 4/4] net/mlx5: replace SMP barriers with C11 barriers Feifei Wang
2021-04-07  1:45 ` [dpdk-dev] [PATCH v1 0/4] refactor SMP barriers for net/mlx Alexander Kozyrev
2021-05-17 10:00 ` [dpdk-dev] [PATCH v2 0/2] remove wmb " Feifei Wang
2021-05-17 10:00   ` [dpdk-dev] [PATCH v2 1/2] net/mlx4: remove unnecessary wmb for Memory Region cache Feifei Wang
2021-05-17 10:00   ` [dpdk-dev] [PATCH v2 2/2] net/mlx5: " Feifei Wang
2021-05-17 14:15     ` Slava Ovsiienko
2021-05-18  8:52       ` [dpdk-dev] 回复: " Feifei Wang
2021-05-18  8:50 ` [dpdk-dev] [PATCH v3 0/2] remove wmb for net/mlx Feifei Wang
2021-05-18  8:50   ` [dpdk-dev] [PATCH v3 1/2] net/mlx4: remove unnecessary wmb for Memory Region cache Feifei Wang
2021-05-18 12:13     ` Slava Ovsiienko
2021-05-18  8:50   ` [dpdk-dev] [PATCH v3 2/2] net/mlx5: " Feifei Wang
2021-05-18 10:17     ` Slava Ovsiienko
2021-05-19  1:54       ` Feifei Wang [this message]
2021-05-27  8:37   ` [dpdk-dev] [PATCH v3 0/2] remove wmb for net/mlx Raslan Darawsheh

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