Change how the quota system computes the total poolsize for temporary storage

storage/browser/quota/quota_settings.cc

Index: storage/browser/quota/quota_settings.cc
diff --git a/storage/browser/quota/quota_settings.cc b/storage/browser/quota/quota_settings.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2b737098de777194d2f887e84e7dba8850ce5af7
--- /dev/null
+++ b/storage/browser/quota/quota_settings.cc
@@ -0,0 +1,83 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "storage/browser/quota/quota_settings.h"
+
+#include <algorithm>
+
+#include "base/metrics/histogram_macros.h"
+#include "base/sys_info.h"
+
+#define UMA_HISTOGRAM_MBYTES(name, sample)                                     \
+  UMA_HISTOGRAM_CUSTOM_COUNTS((name), static_cast<int>((sample) / kMBytes), 1, \

[Ilya Sherman, 2016/11/21 23:25:36]

Optional: Are you sure that you want the metric to start at 1 megabyte?  You
might get better data resolution for the storage sizes that you care about by
starting at something like 100MB.

+                              10 * 1024 * 1024 /* 10TB */, 100)

[Ilya Sherman, 2016/11/21 23:25:36]

I'm not sure that it's worth defining a new macro for just a single invocation,
especially given that there's already a similarly-named macro,
UMA_HISTOGRAM_MEMORY_LARGE_MB (which caps out at a much smaller value, because
it's intended to measure things that sit in RAM).

+
+namespace storage {
+
+base::Optional<storage::QuotaSettings> CalculateNominalDynamicSettings(
+    const base::FilePath& partition_path,
+    bool is_incognito) {
+  const int64_t kMBytes = 1024 * 1024;
+
+  if (is_incognito) {
+    storage::QuotaSettings settings;
+    settings.pool_size =
+        std::min(300 * kMBytes, base::SysInfo::AmountOfPhysicalMemory() / 10);
+    settings.per_host_quota = settings.pool_size / 3;
+    settings.refresh_interval = base::TimeDelta::Max();
+    return settings;
+  }
+
+  // The fraction of the device's storage the browser is willing to
+  // use for temporary storage, this is applied after adjusting the
+  // total to take os_accomodation into account.
+  const double kTemporaryPoolSizeRatio = 1.0 / 3.0;  // 33%
+
+  // The fraction of the device's storage the browser attempts to
+  // keep free.
+  const double kMustRemainAvailableRatio = 0.1;
+
+  // Determines the portion of the temp pool that can be
+  // utilized by a single host (ie. 5 for 20%).
+  const int kPerHostTemporaryPortion = 5;
+
+  // os_accomodation is an estimate of how much storage is needed for
+  // the os and essential application code outside of the browser.
+  const int64_t kDefaultOSAccomodation =
+#if defined(OS_ANDROID)
+      1000 * kMBytes;
+#elif defined(OS_CHROMEOS)
+      1000 * kMBytes;
+#elif defined(OS_WIN) || defined(OS_LINUX) || defined(OS_MACOSX)
+      10000 * kMBytes;
+#else
+#error "Port: Need to define an OS accomodation value for unknown OS."
+#endif
+
+  storage::QuotaSettings settings;
+
+  int64_t total = base::SysInfo::AmountOfTotalDiskSpace(partition_path);
+  if (total == -1) {
+    LOG(ERROR) << "Unable to compute QuotaSettings.";
+    return base::nullopt;
+  }
+
+  // If our hardcoded OS accomodation is too large for the volume size, define
+  // the value as a fraction of the total volume size instead.
+  int64_t os_accomodation =
+      std::min(kDefaultOSAccomodation, static_cast<int64_t>(total * 0.8));
+  UMA_HISTOGRAM_MBYTES("Quota.OSAccomodationDelta",
+                       kDefaultOSAccomodation - os_accomodation);
+
+  int64_t adjusted_total = total - os_accomodation;
+  int64_t pool_size = adjusted_total * kTemporaryPoolSizeRatio;
+
+  settings.pool_size = pool_size;
+  settings.must_remain_available = total * kMustRemainAvailableRatio;
+  settings.per_host_quota = pool_size / kPerHostTemporaryPortion;
+  settings.refresh_interval = base::TimeDelta::FromSeconds(60);
+  return settings;
+}
+
+}  // namespace