Re: [PATCH v2 2/5] xprtrdma: Per-connection pad optimization

[Anna Schumaker <Anna.Schumaker@Netapp.com>]

On 01/24/2017 02:16 PM, Chuck Lever wrote:
> 
>> On Jan 24, 2017, at 2:12 PM, Anna Schumaker <Anna.Schumaker@Netapp.com> wrote:
>>
>> Hi Chuck,
>>
>> On 01/23/2017 03:52 PM, Chuck Lever wrote:
>>> Pad optimization is changed by echoing into
>>> /proc/sys/sunrpc/rdma_pad_optimize. This is a global setting,
>>> affecting all RPC-over-RDMA connections to all servers.
>>>
>>> The marshaling code picks up that value and uses it for decisions
>>> about how to construct each RPC-over-RDMA frame. Having it change
>>> suddenly in mid-operation can result in unexpected failures. And
>>> some servers a client mounts might need chunk round-up, while
>>> others don't.
>>>
>>> So instead, copy the pad_optimize setting into each connection's
>>> rpcrdma_ia when the transport is created, and use the copy, which
>>> can't change during the life of the connection, instead.
>>
>> Does the rdma_pad_optimize option have documentation somewhere that needs to be updated to describe the new behavior?
> 
> I'm not aware of any. No documentation was changed by d5440e27d3e5.

Okay, I just wanted to make sure everything was covered :)

Thanks,
Anna

> 
> 
>> Anna
>>
>>>
>>> This also removes a hack: rpcrdma_convert_iovs was using
>>> the remote-invalidation-expected flag to predict when it could leave
>>> out Write chunk padding. This is because the Linux server handles
>>> implicit XDR padding on Write chunks correctly, and only Linux
>>> servers can set the connection's remote-invalidation-expected flag.
>>>
>>> It's more sensible to use the pad optimization setting instead.
>>>
>>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>>> ---
>>> net/sunrpc/xprtrdma/rpc_rdma.c  |   28 ++++++++++++++--------------
>>> net/sunrpc/xprtrdma/verbs.c     |    1 +
>>> net/sunrpc/xprtrdma/xprt_rdma.h |    1 +
>>> 3 files changed, 16 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
>>> index a524d3c..c634f0f 100644
>>> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
>>> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
>>> @@ -186,9 +186,9 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
>>>  */
>>>
>>> static int
>>> -rpcrdma_convert_iovs(struct xdr_buf *xdrbuf, unsigned int pos,
>>> -	enum rpcrdma_chunktype type, struct rpcrdma_mr_seg *seg,
>>> -	bool reminv_expected)
>>> +rpcrdma_convert_iovs(struct rpcrdma_xprt *r_xprt, struct xdr_buf *xdrbuf,
>>> +		     unsigned int pos, enum rpcrdma_chunktype type,
>>> +		     struct rpcrdma_mr_seg *seg)
>>> {
>>> 	int len, n, p, page_base;
>>> 	struct page **ppages;
>>> @@ -229,14 +229,15 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
>>> 	/* When encoding a Read chunk, the tail iovec contains an
>>> 	 * XDR pad and may be omitted.
>>> 	 */
>>> -	if (type == rpcrdma_readch && xprt_rdma_pad_optimize)
>>> +	if (type == rpcrdma_readch && r_xprt->rx_ia.ri_implicit_roundup)
>>> 		return n;
>>>
>>> -	/* When encoding the Write list, some servers need to see an extra
>>> -	 * segment for odd-length Write chunks. The upper layer provides
>>> -	 * space in the tail iovec for this purpose.
>>> +	/* When encoding a Write chunk, some servers need to see an
>>> +	 * extra segment for non-XDR-aligned Write chunks. The upper
>>> +	 * layer provides space in the tail iovec that may be used
>>> +	 * for this purpose.
>>> 	 */
>>> -	if (type == rpcrdma_writech && reminv_expected)
>>> +	if (type == rpcrdma_writech && r_xprt->rx_ia.ri_implicit_roundup)
>>> 		return n;
>>>
>>> 	if (xdrbuf->tail[0].iov_len) {
>>> @@ -291,7 +292,8 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
>>> 	if (rtype == rpcrdma_areadch)
>>> 		pos = 0;
>>> 	seg = req->rl_segments;
>>> -	nsegs = rpcrdma_convert_iovs(&rqst->rq_snd_buf, pos, rtype, seg, false);
>>> +	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_snd_buf, pos,
>>> +				     rtype, seg);
>>> 	if (nsegs < 0)
>>> 		return ERR_PTR(nsegs);
>>>
>>> @@ -353,10 +355,9 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
>>> 	}
>>>
>>> 	seg = req->rl_segments;
>>> -	nsegs = rpcrdma_convert_iovs(&rqst->rq_rcv_buf,
>>> +	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf,
>>> 				     rqst->rq_rcv_buf.head[0].iov_len,
>>> -				     wtype, seg,
>>> -				     r_xprt->rx_ia.ri_reminv_expected);
>>> +				     wtype, seg);
>>> 	if (nsegs < 0)
>>> 		return ERR_PTR(nsegs);
>>>
>>> @@ -421,8 +422,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
>>> 	}
>>>
>>> 	seg = req->rl_segments;
>>> -	nsegs = rpcrdma_convert_iovs(&rqst->rq_rcv_buf, 0, wtype, seg,
>>> -				     r_xprt->rx_ia.ri_reminv_expected);
>>> +	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf, 0, wtype, seg);
>>> 	if (nsegs < 0)
>>> 		return ERR_PTR(nsegs);
>>>
>>> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
>>> index 11d0774..2a6a367 100644
>>> --- a/net/sunrpc/xprtrdma/verbs.c
>>> +++ b/net/sunrpc/xprtrdma/verbs.c
>>> @@ -208,6 +208,7 @@
>>>
>>> 	/* Default settings for RPC-over-RDMA Version One */
>>> 	r_xprt->rx_ia.ri_reminv_expected = false;
>>> +	r_xprt->rx_ia.ri_implicit_roundup = xprt_rdma_pad_optimize;
>>> 	rsize = RPCRDMA_V1_DEF_INLINE_SIZE;
>>> 	wsize = RPCRDMA_V1_DEF_INLINE_SIZE;
>>>
>>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>>> index e35efd4..c137154 100644
>>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>>> @@ -75,6 +75,7 @@ struct rpcrdma_ia {
>>> 	unsigned int		ri_max_inline_write;
>>> 	unsigned int		ri_max_inline_read;
>>> 	bool			ri_reminv_expected;
>>> +	bool			ri_implicit_roundup;
>>> 	enum ib_mr_type		ri_mrtype;
>>> 	struct ib_qp_attr	ri_qp_attr;
>>> 	struct ib_qp_init_attr	ri_qp_init_attr;
>>>
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> 
> --
> Chuck Lever
> 
> 
>