Reduce the write buffer for leveldb instances associated with Feed

I expect this to have a positive impact on Feed's memory usage.

Bug: 914597
Change-Id: I98b482fdbbf3f3a230902d7764cc32931c2c5784
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1749459
Commit-Queue: Brandon Wylie <wylieb@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686209}

components/feed/core/feed_content_database.cc

@@ -24,8 +24,12 @@ namespace {
 
 const char kContentDatabaseFolder[] = "content";
 
-const size_t kDatabaseWriteBufferSizeBytes = 64 * 1024;                 // 64KB
-const size_t kDatabaseWriteBufferSizeBytesForLowEndDevice = 32 * 1024;  // 32KB
+// Content writes vary a lot in size, loading full page will will have a couple
+// dozen writes totaling a couple dozen KB, but there's a lot of variability.
+// This should result in some batching while also keeping the memory impact very
+// small.
+const size_t kDatabaseWriteBufferSizeBytes = 8 * 1024;                 // 8KB
+const size_t kDatabaseWriteBufferSizeBytesForLowEndDevice = 4 * 1024;  // 4KB
 
 leveldb::ReadOptions CreateReadOptions() {
   leveldb::ReadOptions opts;

components/feed/core/feed_journal_database.cc

@@ -22,8 +22,9 @@ namespace {
 
 const char kJournalDatabaseFolder[] = "journal";
 
-const size_t kDatabaseWriteBufferSizeBytes = 64 * 1024;                 // 64KB
-const size_t kDatabaseWriteBufferSizeBytesForLowEndDevice = 32 * 1024;  // 32KB
+// Journal updates happen infrequently and are typically ~8KB. However there's
+// also one tiny write during startup before more writes that 1KB should handle.
+const size_t kDatabaseWriteBufferSizeBytes = 1 * 1024;  // 1KB
 
 void ReportLoadTimeHistogram(bool success, base::TimeTicks start_time) {
   base::TimeDelta load_time = base::TimeTicks::Now() - start_time;
@@ -69,9 +70,7 @@ bool FeedJournalDatabase::IsInitialized() const {
 
 void FeedJournalDatabase::InitInternal() {
   leveldb_env::Options options = leveldb_proto::CreateSimpleOptions();
-  options.write_buffer_size = base::SysInfo::IsLowEndDevice()
-                                  ? kDatabaseWriteBufferSizeBytesForLowEndDevice
-                                  : kDatabaseWriteBufferSizeBytes;
+  options.write_buffer_size = kDatabaseWriteBufferSizeBytes;
 
   storage_database_->Init(
       options, base::BindOnce(&FeedJournalDatabase::OnDatabaseInitialized,

components/image_fetcher/core/cache/image_metadata_store_leveldb.cc

@@ -36,10 +36,10 @@ int64_t ToDatabaseTime(base::Time time) {
 // The folder where the data will be stored on disk.
 const char kImageDatabaseFolder[] = "cached_image_fetcher_images";
 
-// The amount of data to build up in memory before converting to a sorted on-
-// disk file.
-const size_t kDatabaseWriteBufferSizeBytes = 64 * 1024;                 // 64KB
-const size_t kDatabaseWriteBufferSizeBytesForLowEndDevice = 32 * 1024;  // 32KB
+// Most writes are very small, <100 bytes. This should buffer a handful of them
+// together, but not much more. This should allow a handful of them to be
+// buffered together without causing a significant impact to memory.
+const size_t kDatabaseWriteBufferSizeBytes = 1 * 1024;  // 1KB
 
 bool KeyMatcherFilter(std::string key, const std::string& other_key) {
   return key.compare(other_key) == 0;
@@ -80,11 +80,7 @@ ImageMetadataStoreLevelDB::~ImageMetadataStoreLevelDB() = default;
 
 void ImageMetadataStoreLevelDB::Initialize(base::OnceClosure callback) {
   leveldb_env::Options options = leveldb_proto::CreateSimpleOptions();
-  if (base::SysInfo::IsLowEndDevice()) {
-    options.write_buffer_size = kDatabaseWriteBufferSizeBytesForLowEndDevice;
-  } else {
-    options.write_buffer_size = kDatabaseWriteBufferSizeBytes;
-  }
+  options.write_buffer_size = kDatabaseWriteBufferSizeBytes;
 
   database_->Init(
       options,