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