From a39e4edeaa1635a6d6246bb9de470f046e4856e9 Mon Sep 17 00:00:00 2001
From: Andrei Homescu <ahomescu@google.com>
Date: Fri, 10 Dec 2021 08:41:54 +0000
Subject: binder: Eliminate a data copy in RPC transport operations

Switch RpcTransportRaw to use sendmsg() and recvmsg() over
iovecs to send data from multiple buffers to avoid having
to copy all data into a single large buffer.

Bug: 202878542
Test: atest binderRpcTest
Change-Id: I8ba7fa815040555503160ae41888a0b0efe9e5d2
---
 libs/binder/RpcSession.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'libs/binder/RpcSession.cpp')

diff --git a/libs/binder/RpcSession.cpp b/libs/binder/RpcSession.cpp
index a5a2bb1017..b84395e7cb 100644
--- a/libs/binder/RpcSession.cpp
+++ b/libs/binder/RpcSession.cpp
@@ -615,8 +615,9 @@ status_t RpcSession::initAndAddConnection(unique_fd fd, const std::vector<uint8_
         header.options |= RPC_CONNECTION_OPTION_INCOMING;
     }
 
+    iovec headerIov{&header, sizeof(header)};
     auto sendHeaderStatus =
-            server->interruptableWriteFully(mShutdownTrigger.get(), &header, sizeof(header), {});
+            server->interruptableWriteFully(mShutdownTrigger.get(), &headerIov, 1, {});
     if (sendHeaderStatus != OK) {
         ALOGE("Could not write connection header to socket: %s",
               statusToString(sendHeaderStatus).c_str());
@@ -624,9 +625,10 @@ status_t RpcSession::initAndAddConnection(unique_fd fd, const std::vector<uint8_
     }
 
     if (sessionId.size() > 0) {
+        iovec sessionIov{const_cast<void*>(static_cast<const void*>(sessionId.data())),
+                         sessionId.size()};
         auto sendSessionIdStatus =
-                server->interruptableWriteFully(mShutdownTrigger.get(), sessionId.data(),
-                                                sessionId.size(), {});
+                server->interruptableWriteFully(mShutdownTrigger.get(), &sessionIov, 1, {});
         if (sendSessionIdStatus != OK) {
             ALOGE("Could not write session ID ('%s') to socket: %s",
                   base::HexString(sessionId.data(), sessionId.size()).c_str(),
-- 
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