On Mon, Apr 05, 2021 at 03:41:15PM +0200, Christoph Hellwig wrote: > On Mon, Apr 05, 2021 at 08:23:54AM +0300, Leon Romanovsky wrote: > > From: Leon Romanovsky <leonro@xxxxxxxxxx> > > > > >From Avihai, > > > > Relaxed Ordering is a PCIe mechanism that relaxes the strict ordering > > imposed on PCI transactions, and thus, can improve performance. > > > > Until now, relaxed ordering could be set only by user space applications > > for user MRs. The following patch series enables relaxed ordering for the > > kernel ULPs as well. Relaxed ordering is an optional capability, and as > > such, it is ignored by vendors that don't support it. > > > > The following test results show the performance improvement achieved > > with relaxed ordering. The test was performed on a NVIDIA A100 in order > > to check performance of storage infrastructure over xprtrdma: > > Isn't the Nvidia A100 a GPU not actually supported by Linux at all? > What does that have to do with storage protocols? This system is in use by our storage oriented customer who performed the test. He runs drivers/infiniband/* stack from the upstream, simply backported to specific kernel version. The performance boost is seen in other systems too. > > Also if you enable this for basically all kernel ULPs, why not have > an opt-out into strict ordering for the cases that need it (if there are > any). The RO property is optional, it can only improve. In addition, all in-kernel ULPs don't need strict ordering. I can be mistaken here and Jason will correct me, it is because of two things: ULP doesn't touch data before CQE and DMA API prohibits it. Thanks
