Re: [PATCH v1] svcrdma: Optimize the logic that selects the R_key to invalidate

[Bruce Fields <bfields@fieldses.org>]

On Tue, Nov 27, 2018 at 11:31:23AM -0500, Chuck Lever wrote:
> 
> 
> > On Nov 27, 2018, at 11:29 AM, bfields@fieldses.org wrote:
> > 
> > On Tue, Nov 27, 2018 at 11:11:35AM -0500, Chuck Lever wrote:
> >> o Select the R_key to invalidate while the CPU cache still contains
> >>  the received RPC Call transport header, rather than waiting until
> >>  we're about to send the RPC Reply.
> >> 
> >> o Choose Send With Invalidate if there is exactly one distinct R_key
> >>  in the received transport header. If there's more than one, the
> >>  client will have to perform local invalidation after it has
> >>  already waited for remote invalidation.
> >> 
> >> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> >> ---
> >> Hi-
> >> 
> >> Please consider this NFS server-side patch for v4.21.
> > 
> > OK, thanks, applying.
> > 
> > (By the way, I appreciate it if patch submissions have
> > bfields@fieldses.org on the To: line, my filters handle that a little
> > differently than mailing list traffic.)
> 
> I've been told not to include To: when the patch is being
> presented for review.  This is a v1. If you feel it is ready
> to go in, great! But I purposely did not include To: Bruce
> because it has not had any review yet.

Oh.  The "Please consider this..." made it sound like you wanted it in
now.  I can wait.

--b.

> > --b.
> > 
> >> 
> >> 
> >> include/linux/sunrpc/svc_rdma.h         |    1 
> >> net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |   63 +++++++++++++++++++++++++++++++
> >> net/sunrpc/xprtrdma/svc_rdma_sendto.c   |   53 ++++++--------------------
> >> 3 files changed, 77 insertions(+), 40 deletions(-)
> >> 
> >> diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
> >> index e6e2691..7e22681 100644
> >> --- a/include/linux/sunrpc/svc_rdma.h
> >> +++ b/include/linux/sunrpc/svc_rdma.h
> >> @@ -135,6 +135,7 @@ struct svc_rdma_recv_ctxt {
> >> 	u32			rc_byte_len;
> >> 	unsigned int		rc_page_count;
> >> 	unsigned int		rc_hdr_count;
> >> +	u32			rc_inv_rkey;
> >> 	struct page		*rc_pages[RPCSVC_MAXPAGES];
> >> };
> >> 
> >> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> >> index b24d5b8..828b149 100644
> >> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> >> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> >> @@ -485,6 +485,68 @@ static __be32 *xdr_check_reply_chunk(__be32 *p, const __be32 *end)
> >> 	return p;
> >> }
> >> 
> >> +/* RPC-over-RDMA Version One private extension: Remote Invalidation.
> >> + * Responder's choice: requester signals it can handle Send With
> >> + * Invalidate, and responder chooses one R_key to invalidate.
> >> + *
> >> + * If there is exactly one distinct R_key in the received transport
> >> + * header, set rc_inv_rkey to that R_key. Otherwise, set it to zero.
> >> + *
> >> + * Perform this operation while the received transport header is
> >> + * still in the CPU cache.
> >> + */
> >> +static void svc_rdma_get_inv_rkey(struct svcxprt_rdma *rdma,
> >> +				  struct svc_rdma_recv_ctxt *ctxt)
> >> +{
> >> +	__be32 inv_rkey, *p;
> >> +	u32 i, segcount;
> >> +
> >> +	ctxt->rc_inv_rkey = 0;
> >> +
> >> +	if (!rdma->sc_snd_w_inv)
> >> +		return;
> >> +
> >> +	inv_rkey = xdr_zero;
> >> +	p = ctxt->rc_recv_buf;
> >> +	p += rpcrdma_fixed_maxsz;
> >> +
> >> +	/* Read list */
> >> +	while (*p++ != xdr_zero) {
> >> +		p++;	/* position */
> >> +		if (inv_rkey == xdr_zero)
> >> +			inv_rkey = *p;
> >> +		else if (inv_rkey != *p)
> >> +			return;
> >> +		p += 4;
> >> +	}
> >> +
> >> +	/* Write list */
> >> +	while (*p++ != xdr_zero) {
> >> +		segcount = be32_to_cpup(p++);
> >> +		for (i = 0; i < segcount; i++) {
> >> +			if (inv_rkey == xdr_zero)
> >> +				inv_rkey = *p;
> >> +			else if (inv_rkey != *p)
> >> +				return;
> >> +			p += 4;
> >> +		}
> >> +	}
> >> +
> >> +	/* Reply chunk */
> >> +	if (*p++ != xdr_zero) {
> >> +		segcount = be32_to_cpup(p++);
> >> +		for (i = 0; i < segcount; i++) {
> >> +			if (inv_rkey == xdr_zero)
> >> +				inv_rkey = *p;
> >> +			else if (inv_rkey != *p)
> >> +				return;
> >> +			p += 4;
> >> +		}
> >> +	}
> >> +
> >> +	ctxt->rc_inv_rkey = be32_to_cpu(inv_rkey);
> >> +}
> >> +
> >> /* On entry, xdr->head[0].iov_base points to first byte in the
> >>  * RPC-over-RDMA header.
> >>  *
> >> @@ -746,6 +808,7 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
> >> 		svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
> >> 		return ret;
> >> 	}
> >> +	svc_rdma_get_inv_rkey(rdma_xprt, ctxt);
> >> 
> >> 	p += rpcrdma_fixed_maxsz;
> >> 	if (*p != xdr_zero)
> >> diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> >> index 8602a5f..d48bc6d 100644
> >> --- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> >> +++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> >> @@ -484,32 +484,6 @@ static void svc_rdma_get_write_arrays(__be32 *rdma_argp,
> >> 		*reply = NULL;
> >> }
> >> 
> >> -/* RPC-over-RDMA Version One private extension: Remote Invalidation.
> >> - * Responder's choice: requester signals it can handle Send With
> >> - * Invalidate, and responder chooses one rkey to invalidate.
> >> - *
> >> - * Find a candidate rkey to invalidate when sending a reply.  Picks the
> >> - * first R_key it finds in the chunk lists.
> >> - *
> >> - * Returns zero if RPC's chunk lists are empty.
> >> - */
> >> -static u32 svc_rdma_get_inv_rkey(__be32 *rdma_argp,
> >> -				 __be32 *wr_lst, __be32 *rp_ch)
> >> -{
> >> -	__be32 *p;
> >> -
> >> -	p = rdma_argp + rpcrdma_fixed_maxsz;
> >> -	if (*p != xdr_zero)
> >> -		p += 2;
> >> -	else if (wr_lst && be32_to_cpup(wr_lst + 1))
> >> -		p = wr_lst + 2;
> >> -	else if (rp_ch && be32_to_cpup(rp_ch + 1))
> >> -		p = rp_ch + 2;
> >> -	else
> >> -		return 0;
> >> -	return be32_to_cpup(p);
> >> -}
> >> -
> >> static int svc_rdma_dma_map_page(struct svcxprt_rdma *rdma,
> >> 				 struct svc_rdma_send_ctxt *ctxt,
> >> 				 struct page *page,
> >> @@ -672,7 +646,7 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
> >>  *
> >>  * RDMA Send is the last step of transmitting an RPC reply. Pages
> >>  * involved in the earlier RDMA Writes are here transferred out
> >> - * of the rqstp and into the ctxt's page array. These pages are
> >> + * of the rqstp and into the sctxt's page array. These pages are
> >>  * DMA unmapped by each Write completion, but the subsequent Send
> >>  * completion finally releases these pages.
> >>  *
> >> @@ -680,32 +654,31 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
> >>  * - The Reply's transport header will never be larger than a page.
> >>  */
> >> static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
> >> -				   struct svc_rdma_send_ctxt *ctxt,
> >> -				   __be32 *rdma_argp,
> >> +				   struct svc_rdma_send_ctxt *sctxt,
> >> +				   struct svc_rdma_recv_ctxt *rctxt,
> >> 				   struct svc_rqst *rqstp,
> >> 				   __be32 *wr_lst, __be32 *rp_ch)
> >> {
> >> 	int ret;
> >> 
> >> 	if (!rp_ch) {
> >> -		ret = svc_rdma_map_reply_msg(rdma, ctxt,
> >> +		ret = svc_rdma_map_reply_msg(rdma, sctxt,
> >> 					     &rqstp->rq_res, wr_lst);
> >> 		if (ret < 0)
> >> 			return ret;
> >> 	}
> >> 
> >> -	svc_rdma_save_io_pages(rqstp, ctxt);
> >> +	svc_rdma_save_io_pages(rqstp, sctxt);
> >> 
> >> -	ctxt->sc_send_wr.opcode = IB_WR_SEND;
> >> -	if (rdma->sc_snd_w_inv) {
> >> -		ctxt->sc_send_wr.ex.invalidate_rkey =
> >> -			svc_rdma_get_inv_rkey(rdma_argp, wr_lst, rp_ch);
> >> -		if (ctxt->sc_send_wr.ex.invalidate_rkey)
> >> -			ctxt->sc_send_wr.opcode = IB_WR_SEND_WITH_INV;
> >> +	if (rctxt->rc_inv_rkey) {
> >> +		sctxt->sc_send_wr.opcode = IB_WR_SEND_WITH_INV;
> >> +		sctxt->sc_send_wr.ex.invalidate_rkey = rctxt->rc_inv_rkey;
> >> +	} else {
> >> +		sctxt->sc_send_wr.opcode = IB_WR_SEND;
> >> 	}
> >> 	dprintk("svcrdma: posting Send WR with %u sge(s)\n",
> >> -		ctxt->sc_send_wr.num_sge);
> >> -	return svc_rdma_send(rdma, &ctxt->sc_send_wr);
> >> +		sctxt->sc_send_wr.num_sge);
> >> +	return svc_rdma_send(rdma, &sctxt->sc_send_wr);
> >> }
> >> 
> >> /* Given the client-provided Write and Reply chunks, the server was not
> >> @@ -809,7 +782,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
> >> 	}
> >> 
> >> 	svc_rdma_sync_reply_hdr(rdma, sctxt, svc_rdma_reply_hdr_len(rdma_resp));
> >> -	ret = svc_rdma_send_reply_msg(rdma, sctxt, rdma_argp, rqstp,
> >> +	ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp,
> >> 				      wr_lst, rp_ch);
> >> 	if (ret < 0)
> >> 		goto err1;
> 
> --
> Chuck Lever
> 
>