svcrdma: Avoid releasing a page in svc_xprt_release() (a53d5cb0) · Commits · 戴 / test

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@oracle.com> Signed-off-by:

J. Bruce Fields <bfields@redhat.com>

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -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)

net/sunrpc/xprtrdma/svc_rdma_sendto.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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

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