linux/net/sunrpc/xprtrdma
Chuck Lever b3ce7a25f4 xprtrdma: Avoid Send Queue wrapping
Send WRs can be signalled or unsignalled. A signalled Send WR
always has a matching Send completion, while a unsignalled Send
has a completion only if the Send WR fails.

xprtrdma has a Send account mechanism that is designed to reduce
the number of signalled Send WRs. This in turn mitigates the
interrupt rate of the underlying device.

RDMA consumers can't leave all Sends unsignaled, however, because
providers rely on Send completions to maintain their Send Queue head
and tail pointers. xprtrdma counts the number of unsignaled Send WRs
that have been posted to ensure that Sends are signalled often
enough to prevent the Send Queue from wrapping.

This mechanism neglected to account for FastReg WRs, which are
posted on the Send Queue but never signalled. As a result, the
Send Queue wrapped on occasion, resulting in duplication completions
of FastReg and LocalInv WRs.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
2021-04-26 09:25:43 -04:00
..
backchannel.c xprtrdma: Delete rpcrdma_recv_buffer_put() 2021-04-26 09:24:12 -04:00
frwr_ops.c xprtrdma: Avoid Send Queue wrapping 2021-04-26 09:25:43 -04:00
Makefile svcrdma: Add a "parsed chunk list" data structure 2020-11-30 13:00:22 -05:00
module.c SUNRPC: xprt_load_transport() needs to support the netid "rdma6" 2020-12-02 14:05:52 -05:00
rpc_rdma.c xprtrdma: Do not wake RPC consumer on a failed LocalInv 2021-04-26 09:25:19 -04:00
svc_rdma.c svcrdma: Deprecate stat variables that are no longer used 2021-01-25 09:36:28 -05:00
svc_rdma_backchannel.c svcrdma: disable timeouts on rdma backchannel 2021-03-06 16:41:48 -05:00
svc_rdma_pcl.c svcrdma: Add a "parsed chunk list" data structure 2020-11-30 13:00:22 -05:00
svc_rdma_recvfrom.c svcrdma: Revert "svcrdma: Reduce Receive doorbell rate" 2021-03-11 15:26:07 -05:00
svc_rdma_rw.c svcrdma: Restore read and write stats 2021-01-25 09:36:28 -05:00
svc_rdma_sendto.c svcrdma: Convert rdma_stat_sq_starve to a per-CPU counter 2021-01-25 09:36:28 -05:00
svc_rdma_transport.c svcrdma: Hold private mutex while invoking rdma_accept() 2021-02-15 10:45:00 -05:00
transport.c SUNRPC: Move fault injection call sites 2021-04-14 09:36:29 -04:00
verbs.c xprtrdma: Avoid Send Queue wrapping 2021-04-26 09:25:43 -04:00
xprt_rdma.h xprtrdma: Do not wake RPC consumer on a failed LocalInv 2021-04-26 09:25:19 -04:00