Merge r229894 - WebProcess memory monitor thresholds should be better…

… tuned for embedded systems.

https://bugs.webkit.org/show_bug.cgi?id=183773

Reviewed by Yusuke Suzuki.

Take into account the total system RAM for the thresholds calculation.

For systems with more than 3GB the conservative and strict thresholds remain as they are,
but for systems with less RAM the thresholds are dynamically configured as follows:

- Conservative threshold (release non critical memory) if WebProcess using more than 33% of the total RAM.
- Strict threshold (release all possible memory) if WebProcess using more than 50% of the total RAM.

The Kill threshold is also modified. Now it is capped at 90% of the total RAM.

* wtf/MemoryPressureHandler.cpp:
(WTF::thresholdForMemoryKillWithProcessState):
(WTF::thresholdForPolicy):
(WTF::MemoryPressureHandler::shrinkOrDie):

Source/WTF/ChangeLog

@@ -1,3 +1,25 @@
+2018-03-23  Carlos Alberto Lopez Perez  <clopez@igalia.com>
+
+        WebProcess memory monitor thresholds should be better tuned for embedded systems.
+        https://bugs.webkit.org/show_bug.cgi?id=183773
+
+        Reviewed by Yusuke Suzuki.
+
+        Take into account the total system RAM for the thresholds calculation.
+
+        For systems with more than 3GB the conservative and strict thresholds remain as they are,
+        but for systems with less RAM the thresholds are dynamically configured as follows:
+
+        - Conservative threshold (release non critical memory) if WebProcess using more than 33% of the total RAM.
+        - Strict threshold (release all possible memory) if WebProcess using more than 50% of the total RAM.
+
+        The Kill threshold is also modified. Now it is capped at 90% of the total RAM.
+
+        * wtf/MemoryPressureHandler.cpp:
+        (WTF::thresholdForMemoryKillWithProcessState):
+        (WTF::thresholdForPolicy):
+        (WTF::MemoryPressureHandler::shrinkOrDie):
+
 2018-03-08  Zan Dobersek  <zdobersek@igalia.com>
 
         [GLib] RunLoop::wakeUp(): use a zero value instead of the monotonic time

Source/WTF/wtf/MemoryPressureHandler.cpp

@@ -28,6 +28,7 @@
 
 #include <wtf/MemoryFootprint.h>
 #include <wtf/NeverDestroyed.h>
+#include <wtf/RAMSize.h>
 
 #define LOG_CHANNEL_PREFIX Log
 
@@ -84,20 +85,17 @@ static const char* toString(MemoryUsagePolicy policy)
 
 static size_t thresholdForMemoryKillWithProcessState(WebsamProcessState processState, unsigned tabCount)
 {
+    size_t baseThreshold = 2 * GB;
 #if CPU(X86_64) || CPU(ARM64)
-    size_t baseThreshold;
     if (processState == WebsamProcessState::Active)
         baseThreshold = 4 * GB;
-    else
-        baseThreshold = 2 * GB;
-    if (tabCount <= 1)
-        return baseThreshold;
-    return baseThreshold + (std::min(tabCount - 1, 4u) * 1 * GB);
+    if (tabCount > 1)
+        baseThreshold += std::min(tabCount - 1, 4u) * 1 * GB;
 #else
-    UNUSED_PARAM(processState);
-    UNUSED_PARAM(tabCount);
-    return 3 * GB;
+    if ((tabCount > 1) || (processState == WebsamProcessState::Active))
+        baseThreshold = 3 * GB;
 #endif
+    return std::min(baseThreshold, static_cast<size_t>(ramSize() * 0.9));
 }
 
 void MemoryPressureHandler::setPageCount(unsigned pageCount)
@@ -114,11 +112,12 @@ size_t MemoryPressureHandler::thresholdForMemoryKill()
 
 static size_t thresholdForPolicy(MemoryUsagePolicy policy)
 {
+    const size_t baseThresholdForPolicy = std::min(3 * GB, ramSize());
     switch (policy) {
     case MemoryUsagePolicy::Conservative:
-        return 1 * GB;
+        return baseThresholdForPolicy / 3;
     case MemoryUsagePolicy::Strict:
-        return 1.5 * GB;
+        return baseThresholdForPolicy / 2;
     case MemoryUsagePolicy::Unrestricted:
     default:
         ASSERT_NOT_REACHED();
@@ -150,6 +149,7 @@ void MemoryPressureHandler::shrinkOrDie()
         return;
     }
 
+    WTFLogAlways("Unable to shrink memory footprint of process (%lu MB) below the kill thresold (%lu MB). Killed\n", footprint.value() / MB, thresholdForMemoryKill() / MB);
     RELEASE_ASSERT(m_memoryKillCallback);
     m_memoryKillCallback();
 }