> -----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
