svc_xprt_release() invokes svc_free_res_pages(), which releases pages between rq_respages and rq_next_page. Historically, the RPC/RDMA transport has set these two pointers to be different by one, which means: - one page gets released when svc_recv returns 0. This normally happens whenever one or more RDMA Reads need to be dispatched to complete construction of an RPC Call. - one page gets released after every call to svc_send. In both cases, this released page is immediately refilled by svc_alloc_arg. There does not seem to be a reason for releasing this page. To avoid this unnecessary memory allocator traffic, set rq_next_page more carefully. Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> --- net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 9 ++++++--- net/sunrpc/xprtrdma/svc_rdma_sendto.c | 4 +++- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index 841fca1..ddb7def 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -366,9 +366,6 @@ static void svc_rdma_build_arg_xdr(struct svc_rqst *rqstp, arg->page_base = 0; arg->buflen = ctxt->rc_byte_len; arg->len = ctxt->rc_byte_len; - - rqstp->rq_respages = &rqstp->rq_pages[0]; - rqstp->rq_next_page = rqstp->rq_respages + 1; } /* This accommodates the largest possible Write chunk, @@ -730,6 +727,12 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) svc_rdma_build_arg_xdr(rqstp, ctxt); + /* Prevent svc_xprt_release from releasing pages in rq_pages + * if we return 0 or an error. + */ + rqstp->rq_respages = rqstp->rq_pages; + rqstp->rq_next_page = rqstp->rq_respages; + p = (__be32 *)rqstp->rq_arg.head[0].iov_base; ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg); if (ret < 0) diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c index 4a3efae..b958fb6 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c +++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c @@ -657,7 +657,9 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp, ctxt->sc_pages[i] = rqstp->rq_respages[i]; rqstp->rq_respages[i] = NULL; } - rqstp->rq_next_page = rqstp->rq_respages + 1; + + /* Prevent svc_xprt_release from releasing pages in rq_pages */ + rqstp->rq_next_page = rqstp->rq_respages; } /* Prepare the portion of the RPC Reply that will be transmitted -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
