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author | Chuck Lever <chuck.lever@oracle.com> | 2019-10-17 14:31:53 -0400 |
---|---|---|
committer | Anna Schumaker <Anna.Schumaker@Netapp.com> | 2019-10-24 10:30:40 -0400 |
commit | 614f3c96d7e5efd1c4dc699524857130a52c6a7f (patch) | |
tree | 05b6a845cd5731657b7f63c5af28a597b2bedd38 /net | |
parent | d6764bbd7763fa9d669bba7fc5a50a4bdd8f591b (diff) | |
download | linux-614f3c96d7e5efd1c4dc699524857130a52c6a7f.tar.gz linux-614f3c96d7e5efd1c4dc699524857130a52c6a7f.tar.bz2 linux-614f3c96d7e5efd1c4dc699524857130a52c6a7f.zip |
xprtrdma: Pull up sometimes
On some platforms, DMA mapping part of a page is more costly than
copying bytes. Restore the pull-up code and use that when we
think it's going to be faster. The heuristic for now is to pull-up
when the size of the RPC message body fits in the buffer underlying
the head iovec.
Indeed, not involving the I/O MMU can help the RPC/RDMA transport
scale better for tiny I/Os across more RDMA devices. This is because
interaction with the I/O MMU is eliminated, as is handling a Send
completion, for each of these small I/Os. Without the explicit
unmapping, the NIC no longer needs to do a costly internal TLB shoot
down for buffers that are just a handful of bytes.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net')
-rw-r--r-- | net/sunrpc/xprtrdma/backchannel.c | 2 | ||||
-rw-r--r-- | net/sunrpc/xprtrdma/rpc_rdma.c | 82 | ||||
-rw-r--r-- | net/sunrpc/xprtrdma/verbs.c | 2 | ||||
-rw-r--r-- | net/sunrpc/xprtrdma/xprt_rdma.h | 2 |
4 files changed, 81 insertions, 7 deletions
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c index 50e075fcdd8f..11685245546a 100644 --- a/net/sunrpc/xprtrdma/backchannel.c +++ b/net/sunrpc/xprtrdma/backchannel.c @@ -79,7 +79,7 @@ static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst) *p = xdr_zero; if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN, - &rqst->rq_snd_buf, rpcrdma_noch)) + &rqst->rq_snd_buf, rpcrdma_noch_pullup)) return -EIO; trace_xprtrdma_cb_reply(rqst); diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c index a441dbf9f198..4ad88893e964 100644 --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -392,7 +392,7 @@ static int rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt, unsigned int pos; int nsegs; - if (rtype == rpcrdma_noch) + if (rtype == rpcrdma_noch_pullup || rtype == rpcrdma_noch_mapped) goto done; pos = rqst->rq_snd_buf.head[0].iov_len; @@ -691,6 +691,72 @@ out_mapping_err: return false; } +/* Copy the tail to the end of the head buffer. + */ +static void rpcrdma_pullup_tail_iov(struct rpcrdma_xprt *r_xprt, + struct rpcrdma_req *req, + struct xdr_buf *xdr) +{ + unsigned char *dst; + + dst = (unsigned char *)xdr->head[0].iov_base; + dst += xdr->head[0].iov_len + xdr->page_len; + memmove(dst, xdr->tail[0].iov_base, xdr->tail[0].iov_len); + r_xprt->rx_stats.pullup_copy_count += xdr->tail[0].iov_len; +} + +/* Copy pagelist content into the head buffer. + */ +static void rpcrdma_pullup_pagelist(struct rpcrdma_xprt *r_xprt, + struct rpcrdma_req *req, + struct xdr_buf *xdr) +{ + unsigned int len, page_base, remaining; + struct page **ppages; + unsigned char *src, *dst; + + dst = (unsigned char *)xdr->head[0].iov_base; + dst += xdr->head[0].iov_len; + ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT); + page_base = offset_in_page(xdr->page_base); + remaining = xdr->page_len; + while (remaining) { + src = page_address(*ppages); + src += page_base; + len = min_t(unsigned int, PAGE_SIZE - page_base, remaining); + memcpy(dst, src, len); + r_xprt->rx_stats.pullup_copy_count += len; + + ppages++; + dst += len; + remaining -= len; + page_base = 0; + } +} + +/* Copy the contents of @xdr into @rl_sendbuf and DMA sync it. + * When the head, pagelist, and tail are small, a pull-up copy + * is considerably less costly than DMA mapping the components + * of @xdr. + * + * Assumptions: + * - the caller has already verified that the total length + * of the RPC Call body will fit into @rl_sendbuf. + */ +static bool rpcrdma_prepare_noch_pullup(struct rpcrdma_xprt *r_xprt, + struct rpcrdma_req *req, + struct xdr_buf *xdr) +{ + if (unlikely(xdr->tail[0].iov_len)) + rpcrdma_pullup_tail_iov(r_xprt, req, xdr); + + if (unlikely(xdr->page_len)) + rpcrdma_pullup_pagelist(r_xprt, req, xdr); + + /* The whole RPC message resides in the head iovec now */ + return rpcrdma_prepare_head_iov(r_xprt, req, xdr->len); +} + static bool rpcrdma_prepare_noch_mapped(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req, struct xdr_buf *xdr) @@ -779,7 +845,11 @@ inline int rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt, goto out_unmap; switch (rtype) { - case rpcrdma_noch: + case rpcrdma_noch_pullup: + if (!rpcrdma_prepare_noch_pullup(r_xprt, req, xdr)) + goto out_unmap; + break; + case rpcrdma_noch_mapped: if (!rpcrdma_prepare_noch_mapped(r_xprt, req, xdr)) goto out_unmap; break; @@ -827,6 +897,7 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst) struct rpcrdma_req *req = rpcr_to_rdmar(rqst); struct xdr_stream *xdr = &req->rl_stream; enum rpcrdma_chunktype rtype, wtype; + struct xdr_buf *buf = &rqst->rq_snd_buf; bool ddp_allowed; __be32 *p; int ret; @@ -884,8 +955,9 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst) */ if (rpcrdma_args_inline(r_xprt, rqst)) { *p++ = rdma_msg; - rtype = rpcrdma_noch; - } else if (ddp_allowed && rqst->rq_snd_buf.flags & XDRBUF_WRITE) { + rtype = buf->len < rdmab_length(req->rl_sendbuf) ? + rpcrdma_noch_pullup : rpcrdma_noch_mapped; + } else if (ddp_allowed && buf->flags & XDRBUF_WRITE) { *p++ = rdma_msg; rtype = rpcrdma_readch; } else { @@ -927,7 +999,7 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst) goto out_err; ret = rpcrdma_prepare_send_sges(r_xprt, req, req->rl_hdrbuf.len, - &rqst->rq_snd_buf, rtype); + buf, rtype); if (ret) goto out_err; diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index 2f4658255343..a514e2c89ac3 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -1165,7 +1165,7 @@ int rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt) for (i = 0; i < buf->rb_max_requests; i++) { struct rpcrdma_req *req; - req = rpcrdma_req_create(r_xprt, RPCRDMA_V1_DEF_INLINE_SIZE, + req = rpcrdma_req_create(r_xprt, RPCRDMA_V1_DEF_INLINE_SIZE * 2, GFP_KERNEL); if (!req) goto out; diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h index cdd6a3d43e0f..5d15140a0266 100644 --- a/net/sunrpc/xprtrdma/xprt_rdma.h +++ b/net/sunrpc/xprtrdma/xprt_rdma.h @@ -554,6 +554,8 @@ void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req); enum rpcrdma_chunktype { rpcrdma_noch = 0, + rpcrdma_noch_pullup, + rpcrdma_noch_mapped, rpcrdma_readch, rpcrdma_areadch, rpcrdma_writech, |