> -----Original Message-----
> From: dev <[email protected]> On Behalf Of Feifei Wang
> Sent: Tuesday, May 18, 2021 11:51
> To: Matan Azrad <[email protected]>; Shahaf Shuler
> <[email protected]>
> Cc: [email protected]; [email protected]; Feifei Wang <[email protected]>;
> Ruifeng Wang <[email protected]>
> Subject: [dpdk-dev] [PATCH v3 1/2] net/mlx4: 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 still
> 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]>
