> On Aug 2, 2017, at 3:20 AM, Leon Romanovsky <leon@xxxxxxxxxx> wrote: > > On Tue, Aug 01, 2017 at 05:06:51PM -0400, Chuck Lever wrote: >> Since I converted NFSD to use the new rdma_rw API, I've been >> struggling with how NFSD determines the size of its send CQ, and how >> it provisions its send queue limit (ie, when it waits for more send >> queue entries to become available). >> >> The problem arises because rdma_rw hides the exact number of send >> WQEs it has provisioned. It determines this number based on the MR >> registration mode (FRWR for iWARP devices, local DMA rkey for >> others), but the mode itself is no longer exposed to ULPs. >> >> Thus when FRWR is in use, rdma_rw adds more WQEs, but NFSD is no >> longer aware of this, does not provision a larger CQ, and does not >> raise its send queue accounting limit. That means the extra WQEs are >> never really used. >> >> At LSF this year, Christoph and Sagi proposed a simple API that >> expose information about how many CQ entries are needed so that ULPs >> can provision their CQs more accurately. > > Indeed clean API. Does it make sense to get rid of sc_max_requests and > use this exported value directly? That and sc_[rs]q_depth could now be made local variables in svc_rdma_accept, with a little clean-up work. Eventually I was hoping to make sc_max_requests a true variable so that it could be dynamically reduced to create back pressure on noisy clients. So I hesitate to remove it outright at the moment. >> The first patch here is a pre-requisite for the third. The second >> patch adds the new API. The third patch changes NFSD to use the new >> API to provision its CQ and send queue accounting accurately. >> >> This approach was tested using the (fixed) force_mr core module >> parameter. > > Good, I liked the word "tested" in the sentence :). > >> >> >> --- >> >> Chuck Lever (3): >> svcrdma: Limit RQ depth >> rdma core: Add rdma_rw_mr_payload() >> svcrdma: Estimate Send Queue depth properly >> >> >> drivers/infiniband/core/rw.c | 24 ++++++++++++++++++++ >> include/rdma/rw.h | 2 ++ >> net/sunrpc/xprtrdma/svc_rdma_transport.c | 36 +++++++++++++++++++++--------- >> 3 files changed, 51 insertions(+), 11 deletions(-) >> >> -- >> Chuck Lever >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
