tree 14c8ab8d8f1ba37fc60695382e55a46eac1d2aa1
parent a54d4059e5f356c522aabfd38563ab6e64773263
author Chuck Lever <chuck.lever@oracle.com> 1467222840 -0400
committer Anna Schumaker <Anna.Schumaker@Netapp.com> 1468266643 -0400

xprtrdma: Allocate MRs on demand

Frequent MR list exhaustion can impact I/O throughput, so enough MRs
are always created during transport set-up to prevent running out.
This means more MRs are created than most workloads need.

Commit 94f58c58c0b4 ("xprtrdma: Allow Read list and Reply chunk
simultaneously") introduced support for sending two chunk lists per
RPC, which consumes more MRs per RPC.

Instead of trying to provision more MRs, introduce a mechanism for
allocating MRs on demand. A few MRs are allocated during transport
set-up to kick things off.

This significantly reduces the average number of MRs per transport
while allowing the MR count to grow for workloads or devices that
need more MRs.

FRWR with mlx4 allocated almost 400 MRs per transport before this
patch. Now it starts with 32.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>