> -----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
