mirror of
https://github.com/privatevoid-net/nix-super.git
synced 2024-11-09 15:58:05 +02:00
Factor out GC initialization code
This is not really part of the evaluator: it is just an integration between Boehm GC and Boost coroutines usable for any purpose. The evaluator (merely) optionally uses it.
This commit is contained in:
parent
7c2981fc55
commit
5b53d8fec3
4 changed files with 249 additions and 210 deletions
226
src/libexpr/eval-gc.cc
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226
src/libexpr/eval-gc.cc
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@ -0,0 +1,226 @@
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#include "error.hh"
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#include "environment-variables.hh"
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#include "serialise.hh"
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#include "eval-gc.hh"
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#if HAVE_BOEHMGC
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# include <pthread.h>
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# if __FreeBSD__
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# include <pthread_np.h>
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# endif
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# include <gc/gc.h>
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# include <gc/gc_cpp.h>
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# include <gc/gc_allocator.h>
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# include <boost/coroutine2/coroutine.hpp>
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# include <boost/coroutine2/protected_fixedsize_stack.hpp>
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# include <boost/context/stack_context.hpp>
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#endif
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namespace nix {
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#if HAVE_BOEHMGC
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/* Called when the Boehm GC runs out of memory. */
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static void * oomHandler(size_t requested)
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{
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/* Convert this to a proper C++ exception. */
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throw std::bad_alloc();
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}
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class BoehmGCStackAllocator : public StackAllocator
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{
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boost::coroutines2::protected_fixedsize_stack stack{
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// We allocate 8 MB, the default max stack size on NixOS.
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// A smaller stack might be quicker to allocate but reduces the stack
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// depth available for source filter expressions etc.
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std::max(boost::context::stack_traits::default_size(), static_cast<std::size_t>(8 * 1024 * 1024))};
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// This is specific to boost::coroutines2::protected_fixedsize_stack.
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// The stack protection page is included in sctx.size, so we have to
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// subtract one page size from the stack size.
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std::size_t pfss_usable_stack_size(boost::context::stack_context & sctx)
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{
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return sctx.size - boost::context::stack_traits::page_size();
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}
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public:
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boost::context::stack_context allocate() override
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{
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auto sctx = stack.allocate();
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// Stacks generally start at a high address and grow to lower addresses.
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// Architectures that do the opposite are rare; in fact so rare that
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// boost_routine does not implement it.
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// So we subtract the stack size.
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GC_add_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
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return sctx;
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}
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void deallocate(boost::context::stack_context sctx) override
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{
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GC_remove_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
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stack.deallocate(sctx);
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}
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};
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static BoehmGCStackAllocator boehmGCStackAllocator;
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/**
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* When a thread goes into a coroutine, we lose its original sp until
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* control flow returns to the thread.
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* While in the coroutine, the sp points outside the thread stack,
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* so we can detect this and push the entire thread stack instead,
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* as an approximation.
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* The coroutine's stack is covered by `BoehmGCStackAllocator`.
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* This is not an optimal solution, because the garbage is scanned when a
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* coroutine is active, for both the coroutine and the original thread stack.
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* However, the implementation is quite lean, and usually we don't have active
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* coroutines during evaluation, so this is acceptable.
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*/
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void fixupBoehmStackPointer(void ** sp_ptr, void * _pthread_id)
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{
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void *& sp = *sp_ptr;
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auto pthread_id = reinterpret_cast<pthread_t>(_pthread_id);
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pthread_attr_t pattr;
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size_t osStackSize;
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void * osStackLow;
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void * osStackBase;
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# ifdef __APPLE__
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osStackSize = pthread_get_stacksize_np(pthread_id);
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osStackLow = pthread_get_stackaddr_np(pthread_id);
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# else
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if (pthread_attr_init(&pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_init failed");
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}
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# ifdef HAVE_PTHREAD_GETATTR_NP
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if (pthread_getattr_np(pthread_id, &pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_getattr_np failed");
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}
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# elif HAVE_PTHREAD_ATTR_GET_NP
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if (!pthread_attr_init(&pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_init failed");
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}
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if (!pthread_attr_get_np(pthread_id, &pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_get_np failed");
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}
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# else
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# error "Need one of `pthread_attr_get_np` or `pthread_getattr_np`"
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# endif
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if (pthread_attr_getstack(&pattr, &osStackLow, &osStackSize)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_getstack failed");
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}
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if (pthread_attr_destroy(&pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_destroy failed");
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}
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# endif
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osStackBase = (char *) osStackLow + osStackSize;
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// NOTE: We assume the stack grows down, as it does on all architectures we support.
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// Architectures that grow the stack up are rare.
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if (sp >= osStackBase || sp < osStackLow) { // lo is outside the os stack
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sp = osStackBase;
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}
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}
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/* Disable GC while this object lives. Used by CoroutineContext.
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*
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* Boehm keeps a count of GC_disable() and GC_enable() calls,
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* and only enables GC when the count matches.
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*/
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class BoehmDisableGC
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{
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public:
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BoehmDisableGC()
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{
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GC_disable();
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};
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~BoehmDisableGC()
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{
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GC_enable();
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};
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};
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static inline void initGCReal()
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{
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/* Initialise the Boehm garbage collector. */
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/* Don't look for interior pointers. This reduces the odds of
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misdetection a bit. */
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GC_set_all_interior_pointers(0);
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/* We don't have any roots in data segments, so don't scan from
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there. */
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GC_set_no_dls(1);
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GC_INIT();
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GC_set_oom_fn(oomHandler);
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StackAllocator::defaultAllocator = &boehmGCStackAllocator;
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// TODO: Remove __APPLE__ condition.
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// Comment suggests an implementation that works on darwin and windows
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// https://github.com/ivmai/bdwgc/issues/362#issuecomment-1936672196
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# if GC_VERSION_MAJOR >= 8 && GC_VERSION_MINOR >= 2 && GC_VERSION_MICRO >= 4 && !defined(__APPLE__)
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GC_set_sp_corrector(&fixupBoehmStackPointer);
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if (!GC_get_sp_corrector()) {
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printTalkative("BoehmGC on this platform does not support sp_corrector; will disable GC inside coroutines");
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/* Used to disable GC when entering coroutines on macOS */
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create_coro_gc_hook = []() -> std::shared_ptr<void> { return std::make_shared<BoehmDisableGC>(); };
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}
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# else
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# warning \
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"BoehmGC version does not support GC while coroutine exists. GC will be disabled inside coroutines. Consider updating bdw-gc to 8.2.4 or later."
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# endif
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/* Set the initial heap size to something fairly big (25% of
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physical RAM, up to a maximum of 384 MiB) so that in most cases
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we don't need to garbage collect at all. (Collection has a
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fairly significant overhead.) The heap size can be overridden
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through libgc's GC_INITIAL_HEAP_SIZE environment variable. We
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should probably also provide a nix.conf setting for this. Note
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that GC_expand_hp() causes a lot of virtual, but not physical
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(resident) memory to be allocated. This might be a problem on
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systems that don't overcommit. */
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if (!getEnv("GC_INITIAL_HEAP_SIZE")) {
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size_t size = 32 * 1024 * 1024;
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# if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES)
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size_t maxSize = 384 * 1024 * 1024;
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long pageSize = sysconf(_SC_PAGESIZE);
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long pages = sysconf(_SC_PHYS_PAGES);
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if (pageSize != -1)
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size = (pageSize * pages) / 4; // 25% of RAM
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if (size > maxSize)
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size = maxSize;
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# endif
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debug("setting initial heap size to %1% bytes", size);
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GC_expand_hp(size);
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}
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}
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#endif
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static bool gcInitialised = false;
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void initGC()
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{
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if (gcInitialised)
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return;
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#if HAVE_BOEHMGC
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initGCReal();
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#endif
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gcInitialised = true;
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}
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void assertGCInitialized()
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{
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assert(gcInitialised);
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}
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}
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16
src/libexpr/eval-gc.hh
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16
src/libexpr/eval-gc.hh
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#pragma once
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///@file
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namespace nix {
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/**
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* Initialise the Boehm GC, if applicable.
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*/
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void initGC();
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/**
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* Make sure `initGC` has already been called.
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*/
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void assertGCInitialized();
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}
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#include <boost/container/small_vector.hpp>
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#ifndef _WIN32 // TODO use portable implementation
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# include <sys/resource.h>
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# include <sys/resource.h>
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#endif
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#if HAVE_BOEHMGC
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#define GC_INCLUDE_NEW
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# define GC_INCLUDE_NEW
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#include <pthread.h>
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#if __FreeBSD__
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# include <pthread_np.h>
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#endif
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#include <gc/gc.h>
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#include <gc/gc_cpp.h>
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#include <gc/gc_allocator.h>
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#include <boost/coroutine2/coroutine.hpp>
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#include <boost/coroutine2/protected_fixedsize_stack.hpp>
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#include <boost/context/stack_context.hpp>
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# include <gc/gc.h>
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# include <gc/gc_cpp.h>
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# include <gc/gc_allocator.h>
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#endif
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@ -211,109 +202,6 @@ bool Value::isTrivial() const
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}
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#if HAVE_BOEHMGC
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/* Called when the Boehm GC runs out of memory. */
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static void * oomHandler(size_t requested)
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{
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/* Convert this to a proper C++ exception. */
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throw std::bad_alloc();
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}
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class BoehmGCStackAllocator : public StackAllocator {
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boost::coroutines2::protected_fixedsize_stack stack {
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// We allocate 8 MB, the default max stack size on NixOS.
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// A smaller stack might be quicker to allocate but reduces the stack
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// depth available for source filter expressions etc.
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std::max(boost::context::stack_traits::default_size(), static_cast<std::size_t>(8 * 1024 * 1024))
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};
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// This is specific to boost::coroutines2::protected_fixedsize_stack.
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// The stack protection page is included in sctx.size, so we have to
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// subtract one page size from the stack size.
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std::size_t pfss_usable_stack_size(boost::context::stack_context &sctx) {
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return sctx.size - boost::context::stack_traits::page_size();
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}
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public:
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boost::context::stack_context allocate() override {
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auto sctx = stack.allocate();
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// Stacks generally start at a high address and grow to lower addresses.
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// Architectures that do the opposite are rare; in fact so rare that
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// boost_routine does not implement it.
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// So we subtract the stack size.
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GC_add_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
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return sctx;
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}
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void deallocate(boost::context::stack_context sctx) override {
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GC_remove_roots(static_cast<char *>(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp);
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stack.deallocate(sctx);
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}
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};
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static BoehmGCStackAllocator boehmGCStackAllocator;
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/**
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* When a thread goes into a coroutine, we lose its original sp until
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* control flow returns to the thread.
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* While in the coroutine, the sp points outside the thread stack,
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* so we can detect this and push the entire thread stack instead,
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* as an approximation.
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* The coroutine's stack is covered by `BoehmGCStackAllocator`.
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* This is not an optimal solution, because the garbage is scanned when a
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* coroutine is active, for both the coroutine and the original thread stack.
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* However, the implementation is quite lean, and usually we don't have active
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* coroutines during evaluation, so this is acceptable.
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*/
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void fixupBoehmStackPointer(void ** sp_ptr, void * _pthread_id) {
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void *& sp = *sp_ptr;
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auto pthread_id = reinterpret_cast<pthread_t>(_pthread_id);
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pthread_attr_t pattr;
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size_t osStackSize;
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void * osStackLow;
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void * osStackBase;
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# ifdef __APPLE__
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osStackSize = pthread_get_stacksize_np(pthread_id);
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osStackLow = pthread_get_stackaddr_np(pthread_id);
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# else
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if (pthread_attr_init(&pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_init failed");
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}
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# ifdef HAVE_PTHREAD_GETATTR_NP
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if (pthread_getattr_np(pthread_id, &pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_getattr_np failed");
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}
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# elif HAVE_PTHREAD_ATTR_GET_NP
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if (!pthread_attr_init(&pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_init failed");
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}
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if (!pthread_attr_get_np(pthread_id, &pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_get_np failed");
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}
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# else
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# error "Need one of `pthread_attr_get_np` or `pthread_getattr_np`"
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# endif
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if (pthread_attr_getstack(&pattr, &osStackLow, &osStackSize)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_getstack failed");
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}
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if (pthread_attr_destroy(&pattr)) {
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throw Error("fixupBoehmStackPointer: pthread_attr_destroy failed");
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}
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# endif
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osStackBase = (char *)osStackLow + osStackSize;
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// NOTE: We assume the stack grows down, as it does on all architectures we support.
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// Architectures that grow the stack up are rare.
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if (sp >= osStackBase || sp < osStackLow) { // lo is outside the os stack
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sp = osStackBase;
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}
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}
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#endif
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static Symbol getName(const AttrName & name, EvalState & state, Env & env)
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{
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if (name.symbol) {
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@ -326,92 +214,6 @@ static Symbol getName(const AttrName & name, EvalState & state, Env & env)
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}
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}
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#if HAVE_BOEHMGC
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/* Disable GC while this object lives. Used by CoroutineContext.
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*
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* Boehm keeps a count of GC_disable() and GC_enable() calls,
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* and only enables GC when the count matches.
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*/
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class BoehmDisableGC {
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public:
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BoehmDisableGC() {
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GC_disable();
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};
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~BoehmDisableGC() {
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GC_enable();
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};
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};
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#endif
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static bool gcInitialised = false;
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void initGC()
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{
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if (gcInitialised) return;
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#if HAVE_BOEHMGC
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/* Initialise the Boehm garbage collector. */
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/* Don't look for interior pointers. This reduces the odds of
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misdetection a bit. */
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GC_set_all_interior_pointers(0);
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/* We don't have any roots in data segments, so don't scan from
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there. */
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GC_set_no_dls(1);
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GC_INIT();
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GC_set_oom_fn(oomHandler);
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StackAllocator::defaultAllocator = &boehmGCStackAllocator;
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// TODO: Remove __APPLE__ condition.
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// Comment suggests an implementation that works on darwin and windows
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// https://github.com/ivmai/bdwgc/issues/362#issuecomment-1936672196
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#if GC_VERSION_MAJOR >= 8 && GC_VERSION_MINOR >= 2 && GC_VERSION_MICRO >= 4 && !defined(__APPLE__)
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GC_set_sp_corrector(&fixupBoehmStackPointer);
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if (!GC_get_sp_corrector()) {
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printTalkative("BoehmGC on this platform does not support sp_corrector; will disable GC inside coroutines");
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/* Used to disable GC when entering coroutines on macOS */
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create_coro_gc_hook = []() -> std::shared_ptr<void> {
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return std::make_shared<BoehmDisableGC>();
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};
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}
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#else
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#warning "BoehmGC version does not support GC while coroutine exists. GC will be disabled inside coroutines. Consider updating bdw-gc to 8.2.4 or later."
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#endif
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|
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|
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/* Set the initial heap size to something fairly big (25% of
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physical RAM, up to a maximum of 384 MiB) so that in most cases
|
||||
we don't need to garbage collect at all. (Collection has a
|
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fairly significant overhead.) The heap size can be overridden
|
||||
through libgc's GC_INITIAL_HEAP_SIZE environment variable. We
|
||||
should probably also provide a nix.conf setting for this. Note
|
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that GC_expand_hp() causes a lot of virtual, but not physical
|
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(resident) memory to be allocated. This might be a problem on
|
||||
systems that don't overcommit. */
|
||||
if (!getEnv("GC_INITIAL_HEAP_SIZE")) {
|
||||
size_t size = 32 * 1024 * 1024;
|
||||
#if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES)
|
||||
size_t maxSize = 384 * 1024 * 1024;
|
||||
long pageSize = sysconf(_SC_PAGESIZE);
|
||||
long pages = sysconf(_SC_PHYS_PAGES);
|
||||
if (pageSize != -1)
|
||||
size = (pageSize * pages) / 4; // 25% of RAM
|
||||
if (size > maxSize) size = maxSize;
|
||||
#endif
|
||||
debug("setting initial heap size to %1% bytes", size);
|
||||
GC_expand_hp(size);
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
gcInitialised = true;
|
||||
}
|
||||
|
||||
static constexpr size_t BASE_ENV_SIZE = 128;
|
||||
|
||||
EvalState::EvalState(
|
||||
|
@ -508,7 +310,7 @@ EvalState::EvalState(
|
|||
|
||||
countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
|
||||
|
||||
assert(gcInitialised);
|
||||
assertGCInitialized();
|
||||
|
||||
static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
|
||||
|
||||
|
|
|
@ -3,6 +3,7 @@
|
|||
|
||||
#include "attr-set.hh"
|
||||
#include "eval-error.hh"
|
||||
#include "eval-gc.hh"
|
||||
#include "types.hh"
|
||||
#include "value.hh"
|
||||
#include "nixexpr.hh"
|
||||
|
@ -146,12 +147,6 @@ std::string printValue(EvalState & state, Value & v);
|
|||
std::ostream & operator << (std::ostream & os, const ValueType t);
|
||||
|
||||
|
||||
/**
|
||||
* Initialise the Boehm GC, if applicable.
|
||||
*/
|
||||
void initGC();
|
||||
|
||||
|
||||
struct RegexCache;
|
||||
|
||||
std::shared_ptr<RegexCache> makeRegexCache();
|
||||
|
|
Loading…
Reference in a new issue