Bug 1733054 - Introduce prefs for peak usage pre-incrementation and idle timeout; r=dom-storage-reviewers,asuth

Differential Revision: https://phabricator.services.mozilla.com/D135518

dom/localstorage/ActorsParent.cpp

@@ -2958,6 +2958,21 @@ void SnapshotGradualPrefillPrefChangedCallback(const char* aPrefName,
   gSnapshotGradualPrefill = snapshotGradualPrefill;
 }
 
+int64_t GetSnapshotPeakUsagePreincrement(bool aInitial) {
+  return aInitial ? StaticPrefs::
+                        dom_storage_snapshot_peak_usage_initial_preincrement()
+                  : StaticPrefs::
+                        dom_storage_snapshot_peak_usage_gradual_preincrement();
+}
+
+int64_t GetSnapshotPeakUsageReducedPreincrement(bool aInitial) {
+  return aInitial
+             ? StaticPrefs::
+                   dom_storage_snapshot_peak_usage_reduced_initial_preincrement()
+             : StaticPrefs::
+                   dom_storage_snapshot_peak_usage_reduced_gradual_preincrement();
+}
+
 void ClientValidationPrefChangedCallback(const char* aPrefName,
                                          void* aClosure) {
   MOZ_ASSERT(NS_IsMainThread());
@@ -4961,15 +4976,16 @@ int64_t Datastore::AttemptToUpdateUsage(int64_t aMinSize, bool aInitial) {
   MOZ_ASSERT_IF(aInitial, aMinSize >= 0);
   MOZ_ASSERT_IF(!aInitial, aMinSize > 0);
 
-  const int64_t size = aMinSize + (aInitial ? 131072 : 4096);
+  const int64_t size = aMinSize + GetSnapshotPeakUsagePreincrement(aInitial);
 
-  if (UpdateUsage(size)) {
+  if (size && UpdateUsage(size)) {
     return size;
   }
 
-  const int64_t reducedSize = aMinSize + (aInitial ? 4096 : 1024);
+  const int64_t reducedSize =
+      aMinSize + GetSnapshotPeakUsageReducedPreincrement(aInitial);
 
-  if (UpdateUsage(reducedSize)) {
+  if (reducedSize && UpdateUsage(reducedSize)) {
     return reducedSize;
   }
 

dom/localstorage/LSSnapshot.cpp

@@ -26,6 +26,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/LSValue.h"
@@ -47,12 +48,6 @@
 
 namespace mozilla::dom {
 
-namespace {
-
-const uint32_t kSnapshotIdleTimeoutMs = 20000;
-
-}  // namespace
-
 /**
  * Coalescing manipulation queue used by `LSSnapshot`.  Used by `LSSnapshot` to
  * buffer and coalesce manipulations before they are sent to the parent process,
@@ -1008,7 +1003,8 @@ LSSnapshot::Run() {
     MOZ_ASSERT(mIdleTimer);
 
     MOZ_ALWAYS_SUCCEEDS(mIdleTimer->InitWithNamedFuncCallback(
-        IdleTimerCallback, this, kSnapshotIdleTimeoutMs,
+        IdleTimerCallback, this,
+        StaticPrefs::dom_storage_snapshot_idle_timeout_ms(),
         nsITimer::TYPE_ONE_SHOT, "LSSnapshot::IdleTimerCallback"));
 
     mHasPendingIdleTimerCallback = true;

dom/localstorage/PBackgroundLSDatabase.ipdl

@@ -52,11 +52,12 @@ struct LSSnapshotInitInfo
    * The amount of storage allowed to be used by the Snapshot without requesting
    * more storage space via IncreasePeakUsage.  This is the `initialUsage` plus
    * 0 or more bytes of space.  If space was available, the increase will be the
-   * `minSize` from the PBackgroundLSSnapshot constructor plus peak usage
-   * initial pre-increment.  If the LocalStorage usage was already close to the
-   * limit, then the fallback is either the `minSize` plus peak usage reduced
-   * initial pre-increment, or `minSize`, or 0 depending on remaining available
-   * space.
+   * `minSize` from the PBackgroundLSSnapshot constructor plus the configured
+   * pre-increment (via "dom.storage.snapshot_peak_usage.initial_preincrement").
+   * If the LocalStorage total usage was already close to the limit, then the
+   * fallback is either the `minSize` plus the configured reduced pre-increment
+   * (via "dom.storage.snapshot_peak_usage.reduced_initial_preincrement"), or
+   * `minSize`, or 0 depending on remaining available space.
    */
   int64_t peakUsage;
   // See `LSSnapshot::LoadState` in `LSSnapshot.h`

modules/libpref/init/StaticPrefList.yaml

@@ -3511,6 +3511,46 @@
   mirror: always
   do_not_use_directly: true
 
+# The amount of snapshot peak usage which is attempted to be pre-incremented
+# during snapshot creation.
+- name: dom.storage.snapshot_peak_usage.initial_preincrement
+  type: RelaxedAtomicUint32
+  value: 131072
+  mirror: always
+
+# The amount of snapshot peak usage which is attempted to be pre-incremented
+# during snapshot creation if the LocalStorage usage was already close to the
+# limit (a fallback for dom.storage.snapshot_peak_usage.initial_preincrement).
+- name: dom.storage.snapshot_peak_usage.reduced_initial_preincrement
+  type: RelaxedAtomicUint32
+  value: 4096
+  mirror: always
+
+# The amount of snapshot peak usage which is attempted to be pre-incremented
+# beyond the specific values which are subsequently requested after snapshot
+# creation.
+- name: dom.storage.snapshot_peak_usage.gradual_preincrement
+  type: RelaxedAtomicUint32
+  value: 4096
+  mirror: always
+
+# The amount of snapshot peak usage which is attempted to be pre-incremented
+# beyond the specific values which are subsequently requested after snapshot
+# creation if the LocalStorage total usage was already close to the limit
+# (a fallback for dom.storage.snapshot_peak_usage.gradual_preincrement).
+- name: dom.storage.snapshot_peak_usage.reduced_gradual_preincrement
+  type: RelaxedAtomicUint32
+  value: 1024
+  mirror: always
+
+# How long between a snapshot becomes idle and when we actually finish the
+# snapshot. This preference is only used when "dom.storage.snapshot_reusing"
+# is true.
+- name: dom.storage.snapshot_idle_timeout_ms
+  type: uint32_t
+  value: 20000
+  mirror: always
+
 # Is support for Storage test APIs enabled?
 - name: dom.storage.testing
   type: bool