source: ps/trunk/source/scriptinterface/ScriptContext.cpp@ 25280

/* Copyright (C) 2021 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "precompiled.h"

#include "ScriptContext.h"

#include "lib/alignment.h"
#include "ps/GameSetup/Config.h"
#include "ps/Profile.h"
#include "scriptinterface/ScriptExtraHeaders.h"
#include "scriptinterface/ScriptEngine.h"
#include "scriptinterface/ScriptInterface.h"

void GCSliceCallbackHook(JSContext* UNUSED(cx), JS::GCProgress progress, const JS::GCDescription& UNUSED(desc))
{
    /**
     * From the GCAPI.h file:
     * > During GC, the GC is bracketed by GC_CYCLE_BEGIN/END callbacks. Each
     * > slice between those (whether an incremental or the sole non-incremental
     * > slice) is bracketed by GC_SLICE_BEGIN/GC_SLICE_END.
     * Thus, to safely monitor GCs, we need to profile SLICE_X calls.
     */


    if (progress == JS::GC_SLICE_BEGIN)
    {
        if (CProfileManager::IsInitialised() && Threading::IsMainThread())
            g_Profiler.Start("GCSlice");
        g_Profiler2.RecordRegionEnter("GCSlice");
    }
    else if (progress == JS::GC_SLICE_END)
    {
        if (CProfileManager::IsInitialised() && Threading::IsMainThread())
            g_Profiler.Stop();
        g_Profiler2.RecordRegionLeave();
    }

    // The following code can be used to print some information aobut garbage collection
    // Search for "Nonincremental reason" if there are problems running GC incrementally.
    #if 0
    if (progress == JS::GCProgress::GC_CYCLE_BEGIN)
        printf("starting cycle ===========================================\n");

    const char16_t* str = desc.formatMessage(cx);
    int len = 0;

    for(int i = 0; i < 10000; i++)
    {
        len++;
        if(!str[i])
            break;
    }

    wchar_t outstring[len];

    for(int i = 0; i < len; i++)
    {
        outstring[i] = (wchar_t)str[i];
    }

    printf("---------------------------------------\n: %ls \n---------------------------------------\n", outstring);
    #endif
}

shared_ptr<ScriptContext> ScriptContext::CreateContext(int contextSize, int heapGrowthBytesGCTrigger)
{
    return std::make_shared<ScriptContext>(contextSize, heapGrowthBytesGCTrigger);
}

ScriptContext::ScriptContext(int contextSize, int heapGrowthBytesGCTrigger):
    m_LastGCBytes(0),
    m_LastGCCheck(0.0f),
    m_HeapGrowthBytesGCTrigger(heapGrowthBytesGCTrigger),
    m_ContextSize(contextSize)
{
    ENSURE(ScriptEngine::IsInitialised() && "The ScriptEngine must be initialized before constructing any ScriptContexts!");

    m_cx = JS_NewContext(contextSize);
    ENSURE(m_cx); // TODO: error handling

    // Set stack quota limits - JS scripts will stop with a "too much recursion" exception.
    // This seems to refer to the program's actual stack size, so it should be lower than the lowest common denominator
    // of the various stack sizes of supported OS.
    // From SM78's jsapi.h:
    // - "The stack quotas for each kind of code should be monotonically descending"
    // - "This function may only be called immediately after the runtime is initialized
    //   and before any code is executed and/or interrupts requested"
    JS_SetNativeStackQuota(m_cx, 950 * KiB, 900 * KiB, 850 * KiB);

    ENSURE(JS::InitSelfHostedCode(m_cx));

    JS::SetGCSliceCallback(m_cx, GCSliceCallbackHook);

    JS_SetGCParameter(m_cx, JSGC_MAX_BYTES, m_ContextSize);
    JS_SetGCParameter(m_cx, JSGC_MODE, JSGC_MODE_INCREMENTAL);

    JS_SetOffthreadIonCompilationEnabled(m_cx, true);

    // For GC debugging:
    // JS_SetGCZeal(m_cx, 2, JS_DEFAULT_ZEAL_FREQ);

    JS_SetContextPrivate(m_cx, nullptr);

    JS_SetGlobalJitCompilerOption(m_cx, JSJITCOMPILER_ION_ENABLE, 1);
    JS_SetGlobalJitCompilerOption(m_cx, JSJITCOMPILER_BASELINE_ENABLE, 1);

    JS::ContextOptionsRef(m_cx).setStrictMode(true);

    ScriptEngine::GetSingleton().RegisterContext(m_cx);
}

ScriptContext::~ScriptContext()
{
    ENSURE(ScriptEngine::IsInitialised() && "The ScriptEngine must be active (initialized and not yet shut down) when destroying a ScriptContext!");

    JS_DestroyContext(m_cx);
    ScriptEngine::GetSingleton().UnRegisterContext(m_cx);
}

void ScriptContext::RegisterRealm(JS::Realm* realm)
{
    ENSURE(realm);
    m_Realms.push_back(realm);
}

void ScriptContext::UnRegisterRealm(JS::Realm* realm)
{
    // Schedule the zone for GC, which will destroy the realm.
    if (JS::IsIncrementalGCInProgress(m_cx))
        JS::FinishIncrementalGC(m_cx, JS::GCReason::API);
    JS::PrepareZoneForGC(js::GetRealmZone(realm));
    m_Realms.remove(realm);
}

#define GC_DEBUG_PRINT 0
void ScriptContext::MaybeIncrementalGC(double delay)
{
    PROFILE2("MaybeIncrementalGC");

    if (JS::IsIncrementalGCEnabled(m_cx))
    {
        // The idea is to get the heap size after a completed GC and trigger the next GC when the heap size has
        // reached m_LastGCBytes + X.
        // In practice it doesn't quite work like that. When the incremental marking is completed, the sweeping kicks in.
        // The sweeping actually frees memory and it does this in a background thread (if JS_USE_HELPER_THREADS is set).
        // While the sweeping is happening we already run scripts again and produce new garbage.

        const int GCSliceTimeBudget = 30; // Milliseconds an incremental slice is allowed to run

        // Have a minimum time in seconds to wait between GC slices and before starting a new GC to distribute the GC
        // load and to hopefully make it unnoticeable for the player. This value should be high enough to distribute
        // the load well enough and low enough to make sure we don't run out of memory before we can start with the
        // sweeping.
        if (timer_Time() - m_LastGCCheck < delay)
            return;

        m_LastGCCheck = timer_Time();

        int gcBytes = JS_GetGCParameter(m_cx, JSGC_BYTES);

#if GC_DEBUG_PRINT
            std::cout << "gcBytes: " << gcBytes / 1024 << " KB" << std::endl;
#endif

        if (m_LastGCBytes > gcBytes || m_LastGCBytes == 0)
        {
#if GC_DEBUG_PRINT
            printf("Setting m_LastGCBytes: %d KB \n", gcBytes / 1024);
#endif
            m_LastGCBytes = gcBytes;
        }

        // Run an additional incremental GC slice if the currently running incremental GC isn't over yet
        // ... or
        // start a new incremental GC if the JS heap size has grown enough for a GC to make sense
        if (JS::IsIncrementalGCInProgress(m_cx) || (gcBytes - m_LastGCBytes > m_HeapGrowthBytesGCTrigger))
        {
#if GC_DEBUG_PRINT
            if (JS::IsIncrementalGCInProgress(m_cx))
                printf("An incremental GC cycle is in progress. \n");
            else
                printf("GC needed because JSGC_BYTES - m_LastGCBytes > m_HeapGrowthBytesGCTrigger \n"
                    "    JSGC_BYTES: %d KB \n    m_LastGCBytes: %d KB \n    m_HeapGrowthBytesGCTrigger: %d KB \n",
                    gcBytes / 1024,
                    m_LastGCBytes / 1024,
                    m_HeapGrowthBytesGCTrigger / 1024);
#endif

            // A hack to make sure we never exceed the context size because we can't collect the memory
            // fast enough.
            if (gcBytes > m_ContextSize / 2)
            {
                if (JS::IsIncrementalGCInProgress(m_cx))
                {
#if GC_DEBUG_PRINT
                    printf("Finishing incremental GC because gcBytes > m_ContextSize / 2. \n");
#endif
                    PrepareZonesForIncrementalGC();
                    JS::FinishIncrementalGC(m_cx, JS::GCReason::API);
                }
                else
                {
                    if (gcBytes > m_ContextSize * 0.75)
                    {
                        ShrinkingGC();
#if GC_DEBUG_PRINT
                        printf("Running shrinking GC because gcBytes > m_ContextSize * 0.75. \n");
#endif
                    }
                    else
                    {
#if GC_DEBUG_PRINT
                        printf("Running full GC because gcBytes > m_ContextSize / 2. \n");
#endif
                        JS_GC(m_cx);
                    }
                }
            }
            else
            {
#if GC_DEBUG_PRINT
                if (!JS::IsIncrementalGCInProgress(m_cx))
                    printf("Starting incremental GC \n");
                else
                    printf("Running incremental GC slice \n");
#endif
                PrepareZonesForIncrementalGC();
                if (!JS::IsIncrementalGCInProgress(m_cx))
                    JS::StartIncrementalGC(m_cx, GC_NORMAL, JS::GCReason::API, GCSliceTimeBudget);
                else
                    JS::IncrementalGCSlice(m_cx, JS::GCReason::API, GCSliceTimeBudget);
            }
            m_LastGCBytes = gcBytes;
        }
    }
}

void ScriptContext::ShrinkingGC()
{
    JS_SetGCParameter(m_cx, JSGC_MODE, JSGC_MODE_ZONE);
    JS::PrepareForFullGC(m_cx);
    JS::NonIncrementalGC(m_cx, GC_SHRINK, JS::GCReason::API);
    JS_SetGCParameter(m_cx, JSGC_MODE, JSGC_MODE_INCREMENTAL);
}

void ScriptContext::PrepareZonesForIncrementalGC() const
{
    for (JS::Realm* const& realm : m_Realms)
        JS::PrepareZoneForGC(js::GetRealmZone(realm));
}