Increase the Perfetto page size from 4kb to 32kb

This should reduce the number of Mojo messages sent
to commit chunks from the SMB by a fair amount.

R=ssid@chromium.org

Bug: 966098
Change-Id: If242e37d2b368b93cb7e72079b2958083e4ea749
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1717916
Commit-Queue: oysteine <oysteine@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681912}

content/browser/tracing/startup_tracing_browsertest.cc

@@ -136,7 +136,7 @@ IN_PROC_BROWSER_TEST_F(StartupTracingInProcessTest, TestFilledStartupBuffer) {
     TRACE_EVENT1("toplevel", "bar", "data", std::move(data));
   }
 
-  config.SetTraceBufferSizeInKb(12);
+  config.SetTraceBufferSizeInKb(32);
 
   base::RunLoop wait_for_tracing;
   TracingControllerImpl::GetInstance()->StartTracing(

services/tracing/perfetto/producer_host.cc

@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/process/process.h"
+#include "build/build_config.h"
 #include "services/tracing/perfetto/perfetto_service.h"
 #include "services/tracing/public/cpp/perfetto/producer_client.h"
 #include "services/tracing/public/cpp/perfetto/shared_memory.h"
@@ -18,6 +19,15 @@
 
 namespace tracing {
 
+// TODO(oysteine): Find a good compromise between performance and
+// data granularity (mainly relevant to running with small buffer sizes
+// when we use background tracing) on Android.
+#if defined(OS_ANDROID)
+constexpr size_t kSMBPageSizeInBytes = 4 * 1024;
+#else
+constexpr size_t kSMBPageSizeInBytes = 32 * 1024;
+#endif
+
 ProducerHost::ProducerHost() = default;
 
 ProducerHost::~ProducerHost() {
@@ -59,7 +69,9 @@ void ProducerHost::Initialize(mojom::ProducerClientPtr producer_client,
   // TODO(oysteine): Figure out a good buffer size.
   producer_endpoint_ = service->ConnectProducer(
       this, 0 /* uid */, name,
-      4 * 1024 * 1024 /* shared_memory_size_hint_bytes */, is_in_process_);
+      /*shared_memory_size_hint_bytes=*/4 * 1024 * 1024, is_in_process_,
+      perfetto::TracingService::ProducerSMBScrapingMode::kDefault,
+      /*shared_memory_page_size_hint_bytes=*/kSMBPageSizeInBytes);
   DCHECK(producer_endpoint_);
 }