lib/tsocket: optimize syscalls in tstream_readv_pdu_send()

Once we've got the first part of a pdu we try to optimize
readv calls for the rest of the pdu.

Signed-off-by: Stefan Metzmacher <metze@samba.org>

diff --git a/lib/tsocket/tsocket_helpers.c b/lib/tsocket/tsocket_helpers.c
index 3a41a3efc3df71ee7e7297696e282c158bdb9cbf..809830d79abfdd4e33e1bee8e07e6bc30e5a7d4b 100644 (file)
--- a/lib/tsocket/tsocket_helpers.c
+++ b/lib/tsocket/tsocket_helpers.c
@@ -212,6 +212,20 @@ static void tstream_readv_pdu_ask_for_next_vector(struct tevent_req *req)
        size_t to_read = 0;
        size_t i;
        struct tevent_req *subreq;
+       bool optimize = false;
+       bool save_optimize = false;
+
+       if (state->count > 0) {
+               /*
+                * This is not the first time we asked for a vector,
+                * which means parts of the pdu already arrived.
+                *
+                * In this case it make sense to enable
+                * a syscall/performance optimization if the
+                * low level tstream implementation supports it.
+                */
+               optimize = true;
+       }
 
        TALLOC_FREE(state->vector);
        state->count = 0;
@@ -255,11 +269,26 @@ static void tstream_readv_pdu_ask_for_next_vector(struct tevent_req *req)
                return;
        }
 
+       if (optimize) {
+               /*
+                * If the low level stream is a bsd socket
+                * we will get syscall optimization.
+                *
+                * If it is not a bsd socket
+                * tstream_bsd_optimize_readv() just returns.
+                */
+               save_optimize = tstream_bsd_optimize_readv(state->caller.stream,
+                                                          true);
+       }
        subreq = tstream_readv_send(state,
                                    state->caller.ev,
                                    state->caller.stream,
                                    state->vector,
                                    state->count);
+       if (optimize) {
+               tstream_bsd_optimize_readv(state->caller.stream,
+                                          save_optimize);
+       }
        if (tevent_req_nomem(subreq, req)) {
                return;
        }