Also thanks for your patient communication and explanation. A wonderful discussion~
Best Regards Feifei > -----邮件原件----- > 发件人: Slava Ovsiienko <viachesl...@nvidia.com> > 发送时间: 2021年5月18日 18:18 > 收件人: Feifei Wang <feifei.wa...@arm.com>; Matan Azrad > <ma...@nvidia.com>; Shahaf Shuler <shah...@nvidia.com> > 抄送: dev@dpdk.org; nd <n...@arm.com>; Ruifeng Wang > <ruifeng.w...@arm.com> > 主题: RE: [PATCH v3 2/2] net/mlx5: remove unnecessary wmb for Memory > Region cache > > > -----Original Message----- > > From: Feifei Wang <feifei.wa...@arm.com> > > Sent: Tuesday, May 18, 2021 11:51 > > To: Matan Azrad <ma...@nvidia.com>; Shahaf Shuler > > <shah...@nvidia.com>; Slava Ovsiienko <viachesl...@nvidia.com> > > Cc: dev@dpdk.org; n...@arm.com; Feifei Wang <feifei.wa...@arm.com>; > > Ruifeng Wang <ruifeng.w...@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.w...@arm.com> > > Signed-off-by: Feifei Wang <feifei.wa...@arm.com> > > Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com> > Acked-by: Viacheslav Ovsiienko <viachesl...@nvidia.com> > > Thanks a lot for patience and cooperation. > With best regards, > Slava
