> On Feb 28, 2018, at 5:59 PM, Jason Gunthorpe <jgg@xxxxxxxx> wrote:
>
> On Wed, Feb 28, 2018 at 04:51:11PM -0500, Anna Schumaker wrote:
>>
>>
>> On 02/28/2018 03:30 PM, Chuck Lever wrote:
>>> With FRWR, the client transport can perform memory registration and
>>> post a Send with just a single ib_post_send.
>>>
>>> This reduces contention between the send_request path and the Send
>>> Completion handlers, and reduces the overhead of registering a chunk
>>> that has multiple segments.
>>>
>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>>> net/sunrpc/xprtrdma/fmr_ops.c | 11 ++++++++
>>> net/sunrpc/xprtrdma/frwr_ops.c | 51 +++++++++++++++++++++++++++------------
>>> net/sunrpc/xprtrdma/verbs.c | 3 +-
>>> net/sunrpc/xprtrdma/xprt_rdma.h | 2 ++
>>> 4 files changed, 49 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
>>> index 629e539..5cc68a8 100644
>>> +++ b/net/sunrpc/xprtrdma/fmr_ops.c
>>> @@ -251,6 +251,16 @@ enum {
>>> return ERR_PTR(-EIO);
>>> }
>>>
>>> +/* Post Send WR containing the RPC Call message.
>>> + */
>>> +static int
>>> +fmr_op_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req)
>>> +{
>>> + struct ib_send_wr *bad_wr;
>>> +
>>> + return ib_post_send(ia->ri_id->qp, &req->rl_sendctx->sc_wr, &bad_wr);
>>
>> I wish there was a bad_wr null-check in ib_post_send() (or in the
>> infiniband drivers) so you don't have to declare a variable that's
>> never used again. Coordinating that might be more work than it's
>> worth, though.
>
> It is a good point, I actually don't think we have any user in kernel
> of bad_wr ..
Yes, frwr_op_unmap_sync() uses the 3rd argument, and I'm about to add
a call site for ib_post_recv which uses that argument as well.
> Would prefer to just drop the parameter and add a new function call if
> really, really needed.
You could do something like
ib_post_send_one(qp, wr);
for the common case; and likewise for ib_post_recv.
--
Chuck Lever
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