On Sat, Jul 23, 2016 at 11:02:33AM +0200, Thomas Monjalon wrote: > 2016-07-23 8:05 GMT+02:00 Jerin Jacob <jerin.jacob at caviumnetworks.com>: > > On Thu, Jul 21, 2016 at 11:26:50PM +0200, Thomas Monjalon wrote: > >> > > Consumer queue dequeuing must be guaranteed to be done fully before > >> > > the tail is updated. This is not guaranteed with a read barrier, > >> > > changed to a write barrier just before tail update which in practice > >> > > guarantees correct order of reads and writes. > >> > > > >> > > Signed-off-by: Juhamatti Kuusisaari <juhamatti.kuusisaari at > >> > > coriant.com> > >> > > >> > Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com> > >> > >> Applied, thanks > > > > There was ongoing discussion on this > > http://dpdk.org/ml/archives/dev/2016-July/044168.html > > Sorry Jerin, I forgot this email. > The problem is that nobody replied to your email and you did not nack > the v2 of this patch. > > > This change may not be required as it has the performance impact. > > We need to clearly understand what is the performance impact > (numbers and use cases) on one hand, and is there a real bug fixed > by this patch on the other hand?
IHMO, there is no real bug here. rte_smb_rmb() provides the LOAD-STORE barrier to make sure tail pointer WRITE happens only after prior LOADS. Thoughts? > > Please guys make things clear and we'll revert if needed.
