On Jan 12, 2015, at 11:08 AM, Steve Wise <[email protected]> wrote:
> > >> -----Original Message----- >> From: Chuck Lever [mailto:[email protected]] >> Sent: Sunday, January 11, 2015 6:41 PM >> To: Sagi Grimberg; Steve Wise >> Cc: [email protected]; Linux NFS Mailing List >> Subject: Re: [PATCH v1 06/10] svcrdma: Plant reader function in struct >> svcxprt_rdma >> >> >> On Jan 11, 2015, at 12:45 PM, Sagi Grimberg <[email protected]> wrote: >> >>> On 1/9/2015 9:22 PM, Chuck Lever wrote: >>>> The RDMA reader function doesn't change once an svcxprt is >>>> instantiated. Instead of checking sc_devcap during every incoming >>>> RPC, set the reader function once when the connection is accepted. >>> >>> General question(s), >>> >>> Any specific reason why to use FRMR in the server side? And why only >>> for reads and not writes? Sorry if these are dumb questions... >> >> Steve Wise presented patches a few months back to add FRMR, he >> would have to answer this. Steve has a selection of iWARP adapters >> and maybe could provide some idea of performance impact. I have >> only CX-[23] here. >> > > The rdma rpc server has always tried to use FRMR for rdma reads as far as I > recall. The patch I submitted refactored the design in > order to make it more efficient and to fix some bugs. Unlike IB, the iWARP > protocol only allows 1 target/sink SGE in an rdma read > request message, so an FRMR is used to create that single target/sink SGE > allowing 1 read to be submitted instead of many. How does this work when the client uses PHYSICAL memory registration? It can’t form a read/write list SGE larger than a page, thus the server must emit an RDMA READ or WRITE for each page in the payload. Curious, have you tried using iWARP with PHYSICAL MR on the client? > I > believe that the FRMR allows for more efficient IO since w/o it you end up > with large SGLs of 4K each and lots of read requests. > However, I have no data to back that up. I would think that the write side > (NFS READ) could also benefit from FRMRs too. It also > could use refactoring, because I believe it still creates an intermediate > data structure to hold the write chunks vs just > translating them directly into the RDMA SGLs needed for the IO. See > send_write_chunks() and send_write() and how they create a > svc_rdma_req_map vector first and then translate that into the SGL needed for > the rdma writes. > > >> My next step is to do some performance measurement to see if FRMR >> is worth the trouble, at least with the cards on hand. >> >> I notice that the lcl case does not seem to work with my CX-3 Pro. >> Probably a bug I will have to address first. >> > >> >>> Sagi. >>> >>>> Signed-off-by: Chuck Lever <[email protected]> >>>> --- >>>> >>>> include/linux/sunrpc/svc_rdma.h | 10 ++++ >>>> net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 71 >>>> +++++++++++------------------- >>>> net/sunrpc/xprtrdma/svc_rdma_transport.c | 2 + >>>> 3 files changed, 39 insertions(+), 44 deletions(-) >>>> >>>> diff --git a/include/linux/sunrpc/svc_rdma.h >>>> b/include/linux/sunrpc/svc_rdma.h >>>> index 2280325..f161e30 100644 >>>> --- a/include/linux/sunrpc/svc_rdma.h >>>> +++ b/include/linux/sunrpc/svc_rdma.h >>>> @@ -150,6 +150,10 @@ struct svcxprt_rdma { >>>> struct ib_cq *sc_rq_cq; >>>> struct ib_cq *sc_sq_cq; >>>> struct ib_mr *sc_phys_mr; /* MR for server memory */ >>>> + int (*sc_reader)(struct svcxprt_rdma *, >>>> + struct svc_rqst *, >>>> + struct svc_rdma_op_ctxt *, >>>> + int *, u32 *, u32, u32, u64, bool); >>>> u32 sc_dev_caps; /* distilled device caps */ >>>> u32 sc_dma_lkey; /* local dma key */ >>>> unsigned int sc_frmr_pg_list_len; >>>> @@ -195,6 +199,12 @@ extern int svc_rdma_xdr_get_reply_hdr_len(struct >>>> rpcrdma_msg *); >>>> >>>> /* svc_rdma_recvfrom.c */ >>>> extern int svc_rdma_recvfrom(struct svc_rqst *); >>>> +extern int rdma_read_chunk_lcl(struct svcxprt_rdma *, struct svc_rqst *, >>>> + struct svc_rdma_op_ctxt *, int *, u32 *, >>>> + u32, u32, u64, bool); >>>> +extern int rdma_read_chunk_frmr(struct svcxprt_rdma *, struct svc_rqst *, >>>> + struct svc_rdma_op_ctxt *, int *, u32 *, >>>> + u32, u32, u64, bool); >>>> >>>> /* svc_rdma_sendto.c */ >>>> extern int svc_rdma_sendto(struct svc_rqst *); >>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c >>>> b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c >>>> index 577f865..c3aebc1 100644 >>>> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c >>>> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c >>>> @@ -117,26 +117,16 @@ static int rdma_read_max_sge(struct svcxprt_rdma >>>> *xprt, int sge_count) >>>> return min_t(int, sge_count, xprt->sc_max_sge); >>>> } >>>> >>>> -typedef int (*rdma_reader_fn)(struct svcxprt_rdma *xprt, >>>> - struct svc_rqst *rqstp, >>>> - struct svc_rdma_op_ctxt *head, >>>> - int *page_no, >>>> - u32 *page_offset, >>>> - u32 rs_handle, >>>> - u32 rs_length, >>>> - u64 rs_offset, >>>> - int last); >>>> - >>>> /* Issue an RDMA_READ using the local lkey to map the data sink */ >>>> -static int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt, >>>> - struct svc_rqst *rqstp, >>>> - struct svc_rdma_op_ctxt *head, >>>> - int *page_no, >>>> - u32 *page_offset, >>>> - u32 rs_handle, >>>> - u32 rs_length, >>>> - u64 rs_offset, >>>> - int last) >>>> +int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt, >>>> + struct svc_rqst *rqstp, >>>> + struct svc_rdma_op_ctxt *head, >>>> + int *page_no, >>>> + u32 *page_offset, >>>> + u32 rs_handle, >>>> + u32 rs_length, >>>> + u64 rs_offset, >>>> + bool last) >>>> { >>>> struct ib_send_wr read_wr; >>>> int pages_needed = PAGE_ALIGN(*page_offset + rs_length) >> PAGE_SHIFT; >>>> @@ -221,15 +211,15 @@ static int rdma_read_chunk_lcl(struct svcxprt_rdma >>>> *xprt, >>>> } >>>> >>>> /* Issue an RDMA_READ using an FRMR to map the data sink */ >>>> -static int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt, >>>> - struct svc_rqst *rqstp, >>>> - struct svc_rdma_op_ctxt *head, >>>> - int *page_no, >>>> - u32 *page_offset, >>>> - u32 rs_handle, >>>> - u32 rs_length, >>>> - u64 rs_offset, >>>> - int last) >>>> +int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt, >>>> + struct svc_rqst *rqstp, >>>> + struct svc_rdma_op_ctxt *head, >>>> + int *page_no, >>>> + u32 *page_offset, >>>> + u32 rs_handle, >>>> + u32 rs_length, >>>> + u64 rs_offset, >>>> + bool last) >>>> { >>>> struct ib_send_wr read_wr; >>>> struct ib_send_wr inv_wr; >>>> @@ -374,9 +364,9 @@ static int rdma_read_chunks(struct svcxprt_rdma *xprt, >>>> { >>>> int page_no, ret; >>>> struct rpcrdma_read_chunk *ch; >>>> - u32 page_offset, byte_count; >>>> + u32 handle, page_offset, byte_count; >>>> u64 rs_offset; >>>> - rdma_reader_fn reader; >>>> + bool last; >>>> >>>> /* If no read list is present, return 0 */ >>>> ch = svc_rdma_get_read_chunk(rmsgp); >>>> @@ -399,27 +389,20 @@ static int rdma_read_chunks(struct svcxprt_rdma >>>> *xprt, >>>> head->arg.len = rqstp->rq_arg.len; >>>> head->arg.buflen = rqstp->rq_arg.buflen; >>>> >>>> - /* Use FRMR if supported */ >>>> - if (xprt->sc_dev_caps & SVCRDMA_DEVCAP_FAST_REG) >>>> - reader = rdma_read_chunk_frmr; >>>> - else >>>> - reader = rdma_read_chunk_lcl; >>>> - >>>> page_no = 0; page_offset = 0; >>>> for (ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0]; >>>> ch->rc_discrim != 0; ch++) { >>>> - >>>> + handle = be32_to_cpu(ch->rc_target.rs_handle); >>>> + byte_count = be32_to_cpu(ch->rc_target.rs_length); >>>> xdr_decode_hyper((__be32 *)&ch->rc_target.rs_offset, >>>> &rs_offset); >>>> - byte_count = ntohl(ch->rc_target.rs_length); >>>> >>>> while (byte_count > 0) { >>>> - ret = reader(xprt, rqstp, head, >>>> - &page_no, &page_offset, >>>> - ntohl(ch->rc_target.rs_handle), >>>> - byte_count, rs_offset, >>>> - ((ch+1)->rc_discrim == 0) /* last */ >>>> - ); >>>> + last = (ch + 1)->rc_discrim == xdr_zero; >>>> + ret = xprt->sc_reader(xprt, rqstp, head, >>>> + &page_no, &page_offset, >>>> + handle, byte_count, >>>> + rs_offset, last); >>>> if (ret < 0) >>>> goto err; >>>> byte_count -= ret; >>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c >>>> b/net/sunrpc/xprtrdma/svc_rdma_transport.c >>>> index f2e059b..f609c1c 100644 >>>> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c >>>> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c >>>> @@ -974,10 +974,12 @@ static struct svc_xprt *svc_rdma_accept(struct >>>> svc_xprt *xprt) >>>> * NB: iWARP requires remote write access for the data sink >>>> * of an RDMA_READ. IB does not. >>>> */ >>>> + newxprt->sc_reader = rdma_read_chunk_lcl; >>>> if (devattr.device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS) { >>>> newxprt->sc_frmr_pg_list_len = >>>> devattr.max_fast_reg_page_list_len; >>>> newxprt->sc_dev_caps |= SVCRDMA_DEVCAP_FAST_REG; >>>> + newxprt->sc_reader = rdma_read_chunk_frmr; >>>> } >>>> >>>> /* >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in >>>> the body of a message to [email protected] >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in >>> the body of a message to [email protected] >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> -- >> Chuck Lever >> chuck[dot]lever[at]oracle[dot]com >> > > -- Chuck Lever chuck[dot]lever[at]oracle[dot]com -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
