Reduce memory usage when sending SharedBuffer across IPC

https://bugs.webkit.org/show_bug.cgi?id=248301
rdar://102201837

Pack small SharedBuffers across a single allocated SharedMemory.
A threshold of 4kB has been chosen through educated guesses.
Have URLSchemeTaskDidReceiveData use SharedBuffer when sending data to the content
process rather than a SharedBufferReference. The primary use of a SharedBufferReference
is to keep ownership of the allocated memory to the sending process. There's no
such requirement here.

Fly-by improvement, only perform a single memory allocation when passing a FragmentedShared made of multiple segments
on GTK and WPE platfom.

Reviewed by Kimmo Kinnunen.

* Source/WebKit/Shared/WebCoreArgumentCoders.cpp:
(IPC::useUnixDomainSockets):
(IPC::ArgumentCoder<WebCore::FragmentedSharedBuffer>::encode):
(IPC::ArgumentCoder<WebCore::FragmentedSharedBuffer>::decode):
* Source/WebKit/UIProcess/WebURLSchemeTask.cpp:
(WebKit::WebURLSchemeTask::didReceiveData):
* Source/WebKit/UIProcess/WebURLSchemeTask.h:
* Source/WebKit/WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::urlSchemeTaskDidReceiveData):
* Source/WebKit/WebProcess/WebPage/WebPage.h:
* Source/WebKit/WebProcess/WebPage/WebPage.messages.in:
* Source/WebKit/WebProcess/WebPage/WebURLSchemeHandlerProxy.cpp:
(WebKit::WebURLSchemeHandlerProxy::taskDidReceiveData):
* Source/WebKit/WebProcess/WebPage/WebURLSchemeHandlerProxy.h:

Canonical link: https://commits.webkit.org/256999@main

Source/WebKit/Shared/WebCoreArgumentCoders.cpp

@@ -1806,29 +1806,41 @@ std::optional<SerializedPlatformDataCueValue> ArgumentCoder<WebCore::SerializedP
 }
 #endif
 
+constexpr bool useUnixDomainSockets()
+{
+#if USE(UNIX_DOMAIN_SOCKETS)
+    return true;
+#else
+    return false;
+#endif
+}
+
+static constexpr size_t minimumPageSize = 4096;
+
 void ArgumentCoder<WebCore::FragmentedSharedBuffer>::encode(Encoder& encoder, const WebCore::FragmentedSharedBuffer& buffer)
 {
     uint64_t bufferSize = buffer.size();
     encoder << bufferSize;
     if (!bufferSize)
         return;
 
-#if USE(UNIX_DOMAIN_SOCKETS)
-    // Do not use shared memory for FragmentedSharedBuffer encoding in Unix, because it's easy to reach the
-    // maximum number of file descriptors open per process when sending large data in small chunks
-    // over the IPC. ConnectionUnix.cpp already uses shared memory to send any IPC message that is
-    // too large. See https://bugs.webkit.org/show_bug.cgi?id=208571.
-    for (const auto& element : buffer)
-        encoder.encodeFixedLengthData(element.segment->data(), element.segment->size(), 1);
-#else
-    SharedMemory::Handle handle;
-    {
-        auto sharedMemoryBuffer = SharedMemory::copyBuffer(buffer);
-        if (auto memoryHandle = sharedMemoryBuffer->createHandle(SharedMemory::Protection::ReadOnly))
-            handle = WTFMove(*memoryHandle);
+    if (useUnixDomainSockets() || bufferSize < minimumPageSize) {
+        encoder.reserve(encoder.bufferSize() + bufferSize);
+        // Do not use shared memory for FragmentedSharedBuffer encoding in Unix, because it's easy to reach the
+        // maximum number of file descriptors open per process when sending large data in small chunks
+        // over the IPC. ConnectionUnix.cpp already uses shared memory to send any IPC message that is
+        // too large. See https://bugs.webkit.org/show_bug.cgi?id=208571.
+        for (const auto& element : buffer)
+            encoder.encodeFixedLengthData(element.segment->data(), element.segment->size(), 1);
+    } else {
+        SharedMemory::Handle handle;
+        {
+            auto sharedMemoryBuffer = SharedMemory::copyBuffer(buffer);
+            if (auto memoryHandle = sharedMemoryBuffer->createHandle(SharedMemory::Protection::ReadOnly))
+                handle = WTFMove(*memoryHandle);
+        }
+        encoder << WTFMove(handle);
     }
-    encoder << WTFMove(handle);
-#endif
 }
 
 std::optional<Ref<WebCore::FragmentedSharedBuffer>> ArgumentCoder<WebCore::FragmentedSharedBuffer>::decode(Decoder& decoder)
@@ -1840,17 +1852,18 @@ std::optional<Ref<WebCore::FragmentedSharedBuffer>> ArgumentCoder<WebCore::Fragm
     if (!bufferSize)
         return SharedBuffer::create();
 
-#if USE(UNIX_DOMAIN_SOCKETS)
-    if (!decoder.bufferIsLargeEnoughToContain<uint8_t>(bufferSize))
-        return std::nullopt;
+    if (useUnixDomainSockets() || bufferSize < minimumPageSize) {
+        if (!decoder.bufferIsLargeEnoughToContain<uint8_t>(bufferSize))
+            return std::nullopt;
 
-    Vector<uint8_t> data;
-    data.grow(bufferSize);
-    if (!decoder.decodeFixedLengthData(data.data(), data.size(), 1))
-        return std::nullopt;
+        Vector<uint8_t> data;
+        data.grow(bufferSize);
+        if (!decoder.decodeFixedLengthData(data.data(), data.size(), 1))
+            return std::nullopt;
+
+        return SharedBuffer::create(WTFMove(data));
+    }
 
-    return SharedBuffer::create(WTFMove(data));
-#else
     SharedMemory::Handle handle;
     if (!decoder.decode(handle))
         return std::nullopt;
@@ -1863,7 +1876,6 @@ std::optional<Ref<WebCore::FragmentedSharedBuffer>> ArgumentCoder<WebCore::Fragm
         return std::nullopt;
 
     return SharedBuffer::create(static_cast<unsigned char*>(sharedMemoryBuffer->data()), bufferSize);
-#endif
 }
 
 void ArgumentCoder<WebCore::SharedBuffer>::encode(Encoder& encoder, const WebCore::SharedBuffer& buffer)

Source/WebKit/UIProcess/WebURLSchemeTask.cpp

@@ -167,7 +167,7 @@ auto WebURLSchemeTask::didReceiveResponse(const ResourceResponse& response) -> E
     return ExceptionType::None;
 }
 
-auto WebURLSchemeTask::didReceiveData(const SharedBuffer& buffer) -> ExceptionType
+auto WebURLSchemeTask::didReceiveData(Ref<SharedBuffer>&& buffer) -> ExceptionType
 {
     ASSERT(RunLoop::isMain());
 
@@ -190,7 +190,7 @@ auto WebURLSchemeTask::didReceiveData(const SharedBuffer& buffer) -> ExceptionTy
         return ExceptionType::None;
     }
 
-    m_process->send(Messages::WebPage::URLSchemeTaskDidReceiveData(m_urlSchemeHandler->identifier(), m_resourceLoaderID, IPC::SharedBufferReference(buffer)), m_webPageID);
+    m_process->send(Messages::WebPage::URLSchemeTaskDidReceiveData(m_urlSchemeHandler->identifier(), m_resourceLoaderID, WTFMove(buffer)), m_webPageID);
     return ExceptionType::None;
 }
 

Source/WebKit/UIProcess/WebURLSchemeTask.h

@@ -83,7 +83,7 @@ class WebURLSchemeTask : public API::ObjectImpl<API::Object::Type::URLSchemeTask
     ExceptionType willPerformRedirection(WebCore::ResourceResponse&&, WebCore::ResourceRequest&&,  Function<void(WebCore::ResourceRequest&&)>&&);
     ExceptionType didPerformRedirection(WebCore::ResourceResponse&&, WebCore::ResourceRequest&&);
     ExceptionType didReceiveResponse(const WebCore::ResourceResponse&);
-    ExceptionType didReceiveData(const WebCore::SharedBuffer&);
+    ExceptionType didReceiveData(Ref<WebCore::SharedBuffer>&&);
     ExceptionType didComplete(const WebCore::ResourceError&);
 
     void stop();

Source/WebKit/WebProcess/WebPage/WebPage.cpp

@@ -7406,12 +7406,12 @@ void WebPage::urlSchemeTaskDidReceiveResponse(WebURLSchemeHandlerIdentifier hand
     handler->taskDidReceiveResponse(taskIdentifier, response);
 }
 
-void WebPage::urlSchemeTaskDidReceiveData(WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, const IPC::SharedBufferReference& data)
+void WebPage::urlSchemeTaskDidReceiveData(WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, Ref<WebCore::SharedBuffer>&& data)
 {
     auto* handler = m_identifierToURLSchemeHandlerProxyMap.get(handlerIdentifier);
     ASSERT(handler);
 
-    handler->taskDidReceiveData(taskIdentifier, data.isNull() ? WebCore::SharedBuffer::create() : data.unsafeBuffer().releaseNonNull());
+    handler->taskDidReceiveData(taskIdentifier, WTFMove(data));
 }
 
 void WebPage::urlSchemeTaskDidComplete(WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, const ResourceError& error)

Source/WebKit/WebProcess/WebPage/WebPage.h

@@ -2017,7 +2017,7 @@ class WebPage : public API::ObjectImpl<API::Object::Type::BundlePage>, public IP
     void urlSchemeTaskWillPerformRedirection(WebURLSchemeHandlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, WebCore::ResourceResponse&&, WebCore::ResourceRequest&&, CompletionHandler<void(WebCore::ResourceRequest&&)>&&);
     void urlSchemeTaskDidPerformRedirection(WebURLSchemeHandlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, WebCore::ResourceResponse&&, WebCore::ResourceRequest&&);
     void urlSchemeTaskDidReceiveResponse(WebURLSchemeHandlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, const WebCore::ResourceResponse&);
-    void urlSchemeTaskDidReceiveData(WebURLSchemeHandlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, const IPC::SharedBufferReference&);
+    void urlSchemeTaskDidReceiveData(WebURLSchemeHandlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, Ref<WebCore::SharedBuffer>&&);
     void urlSchemeTaskDidComplete(WebURLSchemeHandlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, const WebCore::ResourceError&);
 
     void setIsTakingSnapshotsForApplicationSuspension(bool);

Source/WebKit/WebProcess/WebPage/WebPage.messages.in

@@ -605,7 +605,7 @@ GenerateSyntheticEditingCommand(enum:uint8_t WebKit::SyntheticEditingCommandType
     URLSchemeTaskWillPerformRedirection(WebKit::WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, WebCore::ResourceResponse response, WebCore::ResourceRequest proposedRequest) -> (WebCore::ResourceRequest actualRequest)
     URLSchemeTaskDidPerformRedirection(WebKit::WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, WebCore::ResourceResponse response, WebCore::ResourceRequest proposedRequest)
     URLSchemeTaskDidReceiveResponse(WebKit::WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, WebCore::ResourceResponse response)
-    URLSchemeTaskDidReceiveData(WebKit::WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, IPC::SharedBufferReference data)
+    URLSchemeTaskDidReceiveData(WebKit::WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, Ref<WebCore::SharedBuffer> data)
     URLSchemeTaskDidComplete(WebKit::WebURLSchemeHandlerIdentifier handlerIdentifier, WebCore::ResourceLoaderIdentifier taskIdentifier, WebCore::ResourceError error)
 
     SetIsSuspended(bool suspended)

Source/WebKit/WebProcess/WebPage/WebURLSchemeHandlerProxy.cpp

@@ -97,13 +97,13 @@ void WebURLSchemeHandlerProxy::taskDidReceiveResponse(WebCore::ResourceLoaderIde
     task->didReceiveResponse(response);
 }
 
-void WebURLSchemeHandlerProxy::taskDidReceiveData(WebCore::ResourceLoaderIdentifier taskIdentifier, const SharedBuffer& data)
+void WebURLSchemeHandlerProxy::taskDidReceiveData(WebCore::ResourceLoaderIdentifier taskIdentifier, Ref<WebCore::SharedBuffer>&& data)
 {
     auto* task = m_tasks.get(taskIdentifier);
     if (!task)
         return;
 
-    task->didReceiveData(data);
+    task->didReceiveData(WTFMove(data));
 }
 
 void WebURLSchemeHandlerProxy::taskDidComplete(WebCore::ResourceLoaderIdentifier taskIdentifier, const ResourceError& error)

Source/WebKit/WebProcess/WebPage/WebURLSchemeHandlerProxy.h

@@ -60,7 +60,7 @@ class WebURLSchemeHandlerProxy : public RefCounted<WebURLSchemeHandlerProxy> {
 
     void taskDidPerformRedirection(WebCore::ResourceLoaderIdentifier, WebCore::ResourceResponse&&, WebCore::ResourceRequest&&, CompletionHandler<void(WebCore::ResourceRequest&&)>&&);
     void taskDidReceiveResponse(WebCore::ResourceLoaderIdentifier, const WebCore::ResourceResponse&);
-    void taskDidReceiveData(WebCore::ResourceLoaderIdentifier, const WebCore::SharedBuffer&);
+    void taskDidReceiveData(WebCore::ResourceLoaderIdentifier, Ref<WebCore::SharedBuffer>&&);
     void taskDidComplete(WebCore::ResourceLoaderIdentifier, const WebCore::ResourceError&);
     void taskDidStopLoading(WebURLSchemeTaskProxy&);