xprtrdma: Reduce context switching due to Local Invalidation

Since commit ba69cd122e ("xprtrdma: Remove support for FMR memory
registration"), FRWR is the only supported memory registration mode.

We can take advantage of the asynchronous nature of FRWR's LOCAL_INV
Work Requests to get rid of the completion wait by having the
LOCAL_INV completion handler take care of DMA unmapping MRs and
waking the upper layer RPC waiter.

This eliminates two context switches when local invalidation is
necessary. As a side benefit, we will no longer need the per-xprt
deferred completion work queue.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2019-06-19 10:33:10 -04:00 committed by Anna Schumaker
parent 40088f0e9b
commit d8099feda4
5 changed files with 137 additions and 53 deletions

View File

@ -712,6 +712,7 @@ TRACE_EVENT(xprtrdma_wc_receive,
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_fastreg);
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li);
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li_wake);
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li_done);
TRACE_EVENT(xprtrdma_frwr_alloc,
TP_PROTO(

View File

@ -542,7 +542,10 @@ static void frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
* @req: rpcrdma_req with a non-empty list of MRs to process
*
* Sleeps until it is safe for the host CPU to access the previously mapped
* memory regions.
* memory regions. This guarantees that registered MRs are properly fenced
* from the server before the RPC consumer accesses the data in them. It
* also ensures proper Send flow control: waking the next RPC waits until
* this RPC has relinquished all its Send Queue entries.
*/
void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
@ -616,3 +619,101 @@ void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
rpcrdma_mr_recycle(mr);
}
}
/**
* frwr_wc_localinv_done - Invoked by RDMA provider for a signaled LOCAL_INV WC
* @cq: completion queue (ignored)
* @wc: completed WR
*
*/
static void frwr_wc_localinv_done(struct ib_cq *cq, struct ib_wc *wc)
{
struct ib_cqe *cqe = wc->wr_cqe;
struct rpcrdma_frwr *frwr =
container_of(cqe, struct rpcrdma_frwr, fr_cqe);
struct rpcrdma_mr *mr = container_of(frwr, struct rpcrdma_mr, frwr);
/* WARNING: Only wr_cqe and status are reliable at this point */
trace_xprtrdma_wc_li_done(wc, frwr);
rpcrdma_complete_rqst(frwr->fr_req->rl_reply);
__frwr_release_mr(wc, mr);
}
/**
* frwr_unmap_async - invalidate memory regions that were registered for @req
* @r_xprt: controlling transport instance
* @req: rpcrdma_req with a non-empty list of MRs to process
*
* This guarantees that registered MRs are properly fenced from the
* server before the RPC consumer accesses the data in them. It also
* ensures proper Send flow control: waking the next RPC waits until
* this RPC has relinquished all its Send Queue entries.
*/
void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
struct ib_send_wr *first, *last, **prev;
const struct ib_send_wr *bad_wr;
struct rpcrdma_frwr *frwr;
struct rpcrdma_mr *mr;
int rc;
/* Chain the LOCAL_INV Work Requests and post them with
* a single ib_post_send() call.
*/
frwr = NULL;
prev = &first;
while (!list_empty(&req->rl_registered)) {
mr = rpcrdma_mr_pop(&req->rl_registered);
trace_xprtrdma_mr_localinv(mr);
r_xprt->rx_stats.local_inv_needed++;
frwr = &mr->frwr;
frwr->fr_cqe.done = frwr_wc_localinv;
frwr->fr_req = req;
last = &frwr->fr_invwr;
last->next = NULL;
last->wr_cqe = &frwr->fr_cqe;
last->sg_list = NULL;
last->num_sge = 0;
last->opcode = IB_WR_LOCAL_INV;
last->send_flags = IB_SEND_SIGNALED;
last->ex.invalidate_rkey = mr->mr_handle;
*prev = last;
prev = &last->next;
}
/* Strong send queue ordering guarantees that when the
* last WR in the chain completes, all WRs in the chain
* are complete. The last completion will wake up the
* RPC waiter.
*/
frwr->fr_cqe.done = frwr_wc_localinv_done;
/* Transport disconnect drains the receive CQ before it
* replaces the QP. The RPC reply handler won't call us
* unless ri_id->qp is a valid pointer.
*/
bad_wr = NULL;
rc = ib_post_send(r_xprt->rx_ia.ri_id->qp, first, &bad_wr);
trace_xprtrdma_post_send(req, rc);
if (!rc)
return;
/* Recycle MRs in the LOCAL_INV chain that did not get posted.
*/
while (bad_wr) {
frwr = container_of(bad_wr, struct rpcrdma_frwr, fr_invwr);
mr = container_of(frwr, struct rpcrdma_mr, frwr);
bad_wr = bad_wr->next;
rpcrdma_mr_recycle(mr);
}
/* The final LOCAL_INV WR in the chain is supposed to
* do the wake. If it was never posted, the wake will
* not happen, so wake here in that case.
*/
rpcrdma_complete_rqst(req->rl_reply);
}

View File

@ -1268,24 +1268,15 @@ out_badheader:
goto out;
}
void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
/* Ensure that any DMA mapped pages associated with
* the Send of the RPC Call have been unmapped before
* allowing the RPC to complete. This protects argument
* memory not controlled by the RPC client from being
* re-used before we're done with it.
*/
static void rpcrdma_release_tx(struct rpcrdma_xprt *r_xprt,
struct rpcrdma_req *req)
{
/* Invalidate and unmap the data payloads before waking
* the waiting application. This guarantees the memory
* regions are properly fenced from the server before the
* application accesses the data. It also ensures proper
* send flow control: waking the next RPC waits until this
* RPC has relinquished all its Send Queue entries.
*/
if (!list_empty(&req->rl_registered))
frwr_unmap_sync(r_xprt, req);
/* Ensure that any DMA mapped pages associated with
* the Send of the RPC Call have been unmapped before
* allowing the RPC to complete. This protects argument
* memory not controlled by the RPC client from being
* re-used before we're done with it.
*/
if (test_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags)) {
r_xprt->rx_stats.reply_waits_for_send++;
out_of_line_wait_on_bit(&req->rl_flags,
@ -1295,24 +1286,23 @@ void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
}
}
/* Reply handling runs in the poll worker thread. Anything that
* might wait is deferred to a separate workqueue.
/**
* rpcrdma_release_rqst - Release hardware resources
* @r_xprt: controlling transport instance
* @req: request with resources to release
*
*/
void rpcrdma_deferred_completion(struct work_struct *work)
void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
struct rpcrdma_rep *rep =
container_of(work, struct rpcrdma_rep, rr_work);
struct rpcrdma_req *req = rpcr_to_rdmar(rep->rr_rqst);
struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
if (!list_empty(&req->rl_registered))
frwr_unmap_sync(r_xprt, req);
trace_xprtrdma_defer_cmp(rep);
if (rep->rr_wc_flags & IB_WC_WITH_INVALIDATE)
frwr_reminv(rep, &req->rl_registered);
rpcrdma_release_rqst(r_xprt, req);
rpcrdma_complete_rqst(rep);
rpcrdma_release_tx(r_xprt, req);
}
/* Process received RPC/RDMA messages.
/**
* rpcrdma_reply_handler - Process received RPC/RDMA messages
* @rep: Incoming rpcrdma_rep object to process
*
* Errors must result in the RPC task either being awakened, or
* allowed to timeout, to discover the errors at that time.
@ -1374,7 +1364,16 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
rep->rr_rqst = rqst;
trace_xprtrdma_reply(rqst->rq_task, rep, req, credits);
queue_work(buf->rb_completion_wq, &rep->rr_work);
if (rep->rr_wc_flags & IB_WC_WITH_INVALIDATE)
frwr_reminv(rep, &req->rl_registered);
if (!list_empty(&req->rl_registered)) {
frwr_unmap_async(r_xprt, req);
/* LocalInv completion will complete the RPC */
} else {
rpcrdma_release_tx(r_xprt, req);
rpcrdma_complete_rqst(rep);
}
return;
out_badversion:

View File

@ -89,14 +89,12 @@ static void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp);
*/
static void rpcrdma_xprt_drain(struct rpcrdma_xprt *r_xprt)
{
struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
struct rpcrdma_ia *ia = &r_xprt->rx_ia;
/* Flush Receives, then wait for deferred Reply work
* to complete.
*/
ib_drain_rq(ia->ri_id->qp);
drain_workqueue(buf->rb_completion_wq);
/* Deferred Reply processing might have scheduled
* local invalidations.
@ -1056,7 +1054,6 @@ static bool rpcrdma_rep_create(struct rpcrdma_xprt *r_xprt, bool temp)
rep->rr_cqe.done = rpcrdma_wc_receive;
rep->rr_rxprt = r_xprt;
INIT_WORK(&rep->rr_work, rpcrdma_deferred_completion);
rep->rr_recv_wr.next = NULL;
rep->rr_recv_wr.wr_cqe = &rep->rr_cqe;
rep->rr_recv_wr.sg_list = &rep->rr_rdmabuf->rg_iov;
@ -1117,15 +1114,6 @@ int rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
if (rc)
goto out;
buf->rb_completion_wq = alloc_workqueue("rpcrdma-%s",
WQ_MEM_RECLAIM | WQ_HIGHPRI,
0,
r_xprt->rx_xprt.address_strings[RPC_DISPLAY_ADDR]);
if (!buf->rb_completion_wq) {
rc = -ENOMEM;
goto out;
}
return 0;
out:
rpcrdma_buffer_destroy(buf);
@ -1199,11 +1187,6 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
{
cancel_delayed_work_sync(&buf->rb_refresh_worker);
if (buf->rb_completion_wq) {
destroy_workqueue(buf->rb_completion_wq);
buf->rb_completion_wq = NULL;
}
rpcrdma_sendctxs_destroy(buf);
while (!list_empty(&buf->rb_recv_bufs)) {

View File

@ -202,10 +202,9 @@ struct rpcrdma_rep {
bool rr_temp;
struct rpcrdma_regbuf *rr_rdmabuf;
struct rpcrdma_xprt *rr_rxprt;
struct work_struct rr_work;
struct rpc_rqst *rr_rqst;
struct xdr_buf rr_hdrbuf;
struct xdr_stream rr_stream;
struct rpc_rqst *rr_rqst;
struct list_head rr_list;
struct ib_recv_wr rr_recv_wr;
};
@ -240,10 +239,12 @@ struct rpcrdma_sendctx {
* An external memory region is any buffer or page that is registered
* on the fly (ie, not pre-registered).
*/
struct rpcrdma_req;
struct rpcrdma_frwr {
struct ib_mr *fr_mr;
struct ib_cqe fr_cqe;
struct completion fr_linv_done;
struct rpcrdma_req *fr_req;
union {
struct ib_reg_wr fr_regwr;
struct ib_send_wr fr_invwr;
@ -388,7 +389,6 @@ struct rpcrdma_buffer {
u32 rb_bc_srv_max_requests;
u32 rb_bc_max_requests;
struct workqueue_struct *rb_completion_wq;
struct delayed_work rb_refresh_worker;
};
@ -561,6 +561,7 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
int frwr_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req);
void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs);
void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req);
void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req);
/*
* RPC/RDMA protocol calls - xprtrdma/rpc_rdma.c
@ -585,7 +586,6 @@ void rpcrdma_complete_rqst(struct rpcrdma_rep *rep);
void rpcrdma_reply_handler(struct rpcrdma_rep *rep);
void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt,
struct rpcrdma_req *req);
void rpcrdma_deferred_completion(struct work_struct *work);
static inline void rpcrdma_set_xdrlen(struct xdr_buf *xdr, size_t len)
{