From fcb3c2a444709d2a53faa20c5b43541674064018 Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Thu, 4 Jan 2024 17:21:40 -0500 Subject: [PATCH] gh-112532: Isolate abandoned segments by interpreter (#113717) * gh-112532: Isolate abandoned segments by interpreter Mimalloc segments are data structures that contain memory allocations along with metadata. Each segment is "owned" by a thread. When a thread exits, it abandons its segments to a global pool to be later reclaimed by other threads. This changes the pool to be per-interpreter instead of process-wide. This will be important for when we use mimalloc to find GC objects in the `--disable-gil` builds. We want heaps to only store Python objects from a single interpreter. Absent this change, the abandoning and reclaiming process could break this isolation. * Add missing '&_mi_abandoned_default' to 'tld_empty' --- Include/internal/mimalloc/mimalloc/internal.h | 20 +--- Include/internal/mimalloc/mimalloc/types.h | 40 ++++++++ Include/internal/pycore_interp.h | 5 + Include/internal/pycore_mimalloc.h | 6 ++ Objects/mimalloc/init.c | 5 +- Objects/mimalloc/segment.c | 97 ++++++++----------- Python/pystate.c | 5 + 7 files changed, 102 insertions(+), 76 deletions(-) diff --git a/Include/internal/mimalloc/mimalloc/internal.h b/Include/internal/mimalloc/mimalloc/internal.h index cb6e211de5b..afd7d18a13e 100644 --- a/Include/internal/mimalloc/mimalloc/internal.h +++ b/Include/internal/mimalloc/mimalloc/internal.h @@ -23,23 +23,6 @@ terms of the MIT license. A copy of the license can be found in the file #define mi_trace_message(...) #endif -#define MI_CACHE_LINE 64 -#if defined(_MSC_VER) -#pragma warning(disable:4127) // suppress constant conditional warning (due to MI_SECURE paths) -#pragma warning(disable:26812) // unscoped enum warning -#define mi_decl_noinline __declspec(noinline) -#define mi_decl_thread __declspec(thread) -#define mi_decl_cache_align __declspec(align(MI_CACHE_LINE)) -#elif (defined(__GNUC__) && (__GNUC__ >= 3)) || defined(__clang__) // includes clang and icc -#define mi_decl_noinline __attribute__((noinline)) -#define mi_decl_thread __thread -#define mi_decl_cache_align __attribute__((aligned(MI_CACHE_LINE))) -#else -#define mi_decl_noinline -#define mi_decl_thread __thread // hope for the best :-) -#define mi_decl_cache_align -#endif - #if defined(__EMSCRIPTEN__) && !defined(__wasi__) #define __wasi__ #endif @@ -131,6 +114,7 @@ void _mi_segment_map_allocated_at(const mi_segment_t* segment); void _mi_segment_map_freed_at(const mi_segment_t* segment); // "segment.c" +extern mi_abandoned_pool_t _mi_abandoned_default; // global abandoned pool mi_page_t* _mi_segment_page_alloc(mi_heap_t* heap, size_t block_size, size_t page_alignment, mi_segments_tld_t* tld, mi_os_tld_t* os_tld); void _mi_segment_page_free(mi_page_t* page, bool force, mi_segments_tld_t* tld); void _mi_segment_page_abandon(mi_page_t* page, mi_segments_tld_t* tld); @@ -145,7 +129,7 @@ void _mi_segment_huge_page_reset(mi_segment_t* segment, mi_page_t* page, m uint8_t* _mi_segment_page_start(const mi_segment_t* segment, const mi_page_t* page, size_t* page_size); // page start for any page void _mi_abandoned_reclaim_all(mi_heap_t* heap, mi_segments_tld_t* tld); -void _mi_abandoned_await_readers(void); +void _mi_abandoned_await_readers(mi_abandoned_pool_t *pool); void _mi_abandoned_collect(mi_heap_t* heap, bool force, mi_segments_tld_t* tld); // "page.c" diff --git a/Include/internal/mimalloc/mimalloc/types.h b/Include/internal/mimalloc/mimalloc/types.h index 7616f37e4b9..ab41b1ce990 100644 --- a/Include/internal/mimalloc/mimalloc/types.h +++ b/Include/internal/mimalloc/mimalloc/types.h @@ -33,6 +33,23 @@ terms of the MIT license. A copy of the license can be found in the file #define MI_MAX_ALIGN_SIZE 16 // sizeof(max_align_t) #endif +#define MI_CACHE_LINE 64 +#if defined(_MSC_VER) +#pragma warning(disable:4127) // suppress constant conditional warning (due to MI_SECURE paths) +#pragma warning(disable:26812) // unscoped enum warning +#define mi_decl_noinline __declspec(noinline) +#define mi_decl_thread __declspec(thread) +#define mi_decl_cache_align __declspec(align(MI_CACHE_LINE)) +#elif (defined(__GNUC__) && (__GNUC__ >= 3)) || defined(__clang__) // includes clang and icc +#define mi_decl_noinline __attribute__((noinline)) +#define mi_decl_thread __thread +#define mi_decl_cache_align __attribute__((aligned(MI_CACHE_LINE))) +#else +#define mi_decl_noinline +#define mi_decl_thread __thread // hope for the best :-) +#define mi_decl_cache_align +#endif + // ------------------------------------------------------ // Variants // ------------------------------------------------------ @@ -445,6 +462,28 @@ typedef struct mi_segment_s { mi_slice_t slices[MI_SLICES_PER_SEGMENT+1]; // one more for huge blocks with large alignment } mi_segment_t; +typedef uintptr_t mi_tagged_segment_t; + +// Segments unowned by any thread are put in a shared pool +typedef struct mi_abandoned_pool_s { + // This is a list of visited abandoned pages that were full at the time. + // this list migrates to `abandoned` when that becomes NULL. The use of + // this list reduces contention and the rate at which segments are visited. + mi_decl_cache_align _Atomic(mi_segment_t*) abandoned_visited; // = NULL + + // The abandoned page list (tagged as it supports pop) + mi_decl_cache_align _Atomic(mi_tagged_segment_t) abandoned; // = NULL + + // Maintain these for debug purposes (these counts may be a bit off) + mi_decl_cache_align _Atomic(size_t) abandoned_count; + mi_decl_cache_align _Atomic(size_t) abandoned_visited_count; + + // We also maintain a count of current readers of the abandoned list + // in order to prevent resetting/decommitting segment memory if it might + // still be read. + mi_decl_cache_align _Atomic(size_t) abandoned_readers; // = 0 +} mi_abandoned_pool_t; + // ------------------------------------------------------ // Heaps @@ -654,6 +693,7 @@ typedef struct mi_segments_tld_s { size_t peak_size; // peak size of all segments mi_stats_t* stats; // points to tld stats mi_os_tld_t* os; // points to os stats + mi_abandoned_pool_t* abandoned; // pool of abandoned segments } mi_segments_tld_t; // Thread local data diff --git a/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h index 04d7a6a615e..4512b1edb4b 100644 --- a/Include/internal/pycore_interp.h +++ b/Include/internal/pycore_interp.h @@ -27,6 +27,7 @@ extern "C" { #include "pycore_import.h" // struct _import_state #include "pycore_instruments.h" // _PY_MONITORING_EVENTS #include "pycore_list.h" // struct _Py_list_state +#include "pycore_mimalloc.h" // struct _mimalloc_interp_state #include "pycore_object_state.h" // struct _py_object_state #include "pycore_obmalloc.h" // struct _obmalloc_state #include "pycore_tstate.h" // _PyThreadStateImpl @@ -166,6 +167,10 @@ struct _is { struct _warnings_runtime_state warnings; struct atexit_state atexit; +#if defined(Py_GIL_DISABLED) + struct _mimalloc_interp_state mimalloc; +#endif + struct _obmalloc_state obmalloc; PyObject *audit_hooks; diff --git a/Include/internal/pycore_mimalloc.h b/Include/internal/pycore_mimalloc.h index adebb559dae..1e7ed5a4ca6 100644 --- a/Include/internal/pycore_mimalloc.h +++ b/Include/internal/pycore_mimalloc.h @@ -35,6 +35,12 @@ typedef enum { #endif #ifdef Py_GIL_DISABLED +struct _mimalloc_interp_state { + // When exiting, threads place any segments with live blocks in this + // shared pool for other threads to claim and reuse. + mi_abandoned_pool_t abandoned_pool; +}; + struct _mimalloc_thread_state { mi_heap_t *current_object_heap; mi_heap_t heaps[_Py_MIMALLOC_HEAP_COUNT]; diff --git a/Objects/mimalloc/init.c b/Objects/mimalloc/init.c index 376e14b49b7..0446021fdc5 100644 --- a/Objects/mimalloc/init.c +++ b/Objects/mimalloc/init.c @@ -131,7 +131,7 @@ mi_decl_cache_align static const mi_tld_t tld_empty = { 0, false, NULL, NULL, - { MI_SEGMENT_SPAN_QUEUES_EMPTY, 0, 0, 0, 0, tld_empty_stats, tld_empty_os }, // segments + { MI_SEGMENT_SPAN_QUEUES_EMPTY, 0, 0, 0, 0, tld_empty_stats, tld_empty_os, &_mi_abandoned_default }, // segments { 0, tld_empty_stats }, // os { MI_STATS_NULL } // stats }; @@ -148,7 +148,7 @@ extern mi_heap_t _mi_heap_main; static mi_tld_t tld_main = { 0, false, &_mi_heap_main, & _mi_heap_main, - { MI_SEGMENT_SPAN_QUEUES_EMPTY, 0, 0, 0, 0, &tld_main.stats, &tld_main.os }, // segments + { MI_SEGMENT_SPAN_QUEUES_EMPTY, 0, 0, 0, 0, &tld_main.stats, &tld_main.os, &_mi_abandoned_default }, // segments { 0, &tld_main.stats }, // os { MI_STATS_NULL } // stats }; @@ -308,6 +308,7 @@ void _mi_tld_init(mi_tld_t* tld, mi_heap_t* bheap) { _mi_memcpy_aligned(tld, &tld_empty, sizeof(*tld)); tld->segments.stats = &tld->stats; tld->segments.os = &tld->os; + tld->segments.abandoned = &_mi_abandoned_default; tld->os.stats = &tld->stats; tld->heap_backing = bheap; tld->heaps = bheap; diff --git a/Objects/mimalloc/segment.c b/Objects/mimalloc/segment.c index 033e0f97c36..1040da0d9af 100644 --- a/Objects/mimalloc/segment.c +++ b/Objects/mimalloc/segment.c @@ -395,7 +395,7 @@ static void mi_segment_os_free(mi_segment_t* segment, mi_segments_tld_t* tld) { const size_t size = mi_segment_size(segment); const size_t csize = _mi_commit_mask_committed_size(&segment->commit_mask, size); - _mi_abandoned_await_readers(); // wait until safe to free + _mi_abandoned_await_readers(tld->abandoned); // wait until safe to free _mi_arena_free(segment, mi_segment_size(segment), csize, segment->memid, tld->stats); } @@ -1059,7 +1059,6 @@ would be spread among all other segments in the arenas. // Use the bottom 20-bits (on 64-bit) of the aligned segment pointers // to put in a tag that increments on update to avoid the A-B-A problem. #define MI_TAGGED_MASK MI_SEGMENT_MASK -typedef uintptr_t mi_tagged_segment_t; static mi_segment_t* mi_tagged_segment_ptr(mi_tagged_segment_t ts) { return (mi_segment_t*)(ts & ~MI_TAGGED_MASK); @@ -1071,55 +1070,40 @@ static mi_tagged_segment_t mi_tagged_segment(mi_segment_t* segment, mi_tagged_se return ((uintptr_t)segment | tag); } -// This is a list of visited abandoned pages that were full at the time. -// this list migrates to `abandoned` when that becomes NULL. The use of -// this list reduces contention and the rate at which segments are visited. -static mi_decl_cache_align _Atomic(mi_segment_t*) abandoned_visited; // = NULL - -// The abandoned page list (tagged as it supports pop) -static mi_decl_cache_align _Atomic(mi_tagged_segment_t) abandoned; // = NULL - -// Maintain these for debug purposes (these counts may be a bit off) -static mi_decl_cache_align _Atomic(size_t) abandoned_count; -static mi_decl_cache_align _Atomic(size_t) abandoned_visited_count; - -// We also maintain a count of current readers of the abandoned list -// in order to prevent resetting/decommitting segment memory if it might -// still be read. -static mi_decl_cache_align _Atomic(size_t) abandoned_readers; // = 0 +mi_abandoned_pool_t _mi_abandoned_default; // Push on the visited list -static void mi_abandoned_visited_push(mi_segment_t* segment) { +static void mi_abandoned_visited_push(mi_abandoned_pool_t *pool, mi_segment_t* segment) { mi_assert_internal(segment->thread_id == 0); mi_assert_internal(mi_atomic_load_ptr_relaxed(mi_segment_t,&segment->abandoned_next) == NULL); mi_assert_internal(segment->next == NULL); mi_assert_internal(segment->used > 0); - mi_segment_t* anext = mi_atomic_load_ptr_relaxed(mi_segment_t, &abandoned_visited); + mi_segment_t* anext = mi_atomic_load_ptr_relaxed(mi_segment_t, &pool->abandoned_visited); do { mi_atomic_store_ptr_release(mi_segment_t, &segment->abandoned_next, anext); - } while (!mi_atomic_cas_ptr_weak_release(mi_segment_t, &abandoned_visited, &anext, segment)); - mi_atomic_increment_relaxed(&abandoned_visited_count); + } while (!mi_atomic_cas_ptr_weak_release(mi_segment_t, &pool->abandoned_visited, &anext, segment)); + mi_atomic_increment_relaxed(&pool->abandoned_visited_count); } // Move the visited list to the abandoned list. -static bool mi_abandoned_visited_revisit(void) +static bool mi_abandoned_visited_revisit(mi_abandoned_pool_t *pool) { // quick check if the visited list is empty - if (mi_atomic_load_ptr_relaxed(mi_segment_t, &abandoned_visited) == NULL) return false; + if (mi_atomic_load_ptr_relaxed(mi_segment_t, &pool->abandoned_visited) == NULL) return false; // grab the whole visited list - mi_segment_t* first = mi_atomic_exchange_ptr_acq_rel(mi_segment_t, &abandoned_visited, NULL); + mi_segment_t* first = mi_atomic_exchange_ptr_acq_rel(mi_segment_t, &pool->abandoned_visited, NULL); if (first == NULL) return false; // first try to swap directly if the abandoned list happens to be NULL mi_tagged_segment_t afirst; - mi_tagged_segment_t ts = mi_atomic_load_relaxed(&abandoned); + mi_tagged_segment_t ts = mi_atomic_load_relaxed(&pool->abandoned); if (mi_tagged_segment_ptr(ts)==NULL) { - size_t count = mi_atomic_load_relaxed(&abandoned_visited_count); + size_t count = mi_atomic_load_relaxed(&pool->abandoned_visited_count); afirst = mi_tagged_segment(first, ts); - if (mi_atomic_cas_strong_acq_rel(&abandoned, &ts, afirst)) { - mi_atomic_add_relaxed(&abandoned_count, count); - mi_atomic_sub_relaxed(&abandoned_visited_count, count); + if (mi_atomic_cas_strong_acq_rel(&pool->abandoned, &ts, afirst)) { + mi_atomic_add_relaxed(&pool->abandoned_count, count); + mi_atomic_sub_relaxed(&pool->abandoned_visited_count, count); return true; } } @@ -1133,51 +1117,51 @@ static bool mi_abandoned_visited_revisit(void) // and atomically prepend to the abandoned list // (no need to increase the readers as we don't access the abandoned segments) - mi_tagged_segment_t anext = mi_atomic_load_relaxed(&abandoned); + mi_tagged_segment_t anext = mi_atomic_load_relaxed(&pool->abandoned); size_t count; do { - count = mi_atomic_load_relaxed(&abandoned_visited_count); + count = mi_atomic_load_relaxed(&pool->abandoned_visited_count); mi_atomic_store_ptr_release(mi_segment_t, &last->abandoned_next, mi_tagged_segment_ptr(anext)); afirst = mi_tagged_segment(first, anext); - } while (!mi_atomic_cas_weak_release(&abandoned, &anext, afirst)); - mi_atomic_add_relaxed(&abandoned_count, count); - mi_atomic_sub_relaxed(&abandoned_visited_count, count); + } while (!mi_atomic_cas_weak_release(&pool->abandoned, &anext, afirst)); + mi_atomic_add_relaxed(&pool->abandoned_count, count); + mi_atomic_sub_relaxed(&pool->abandoned_visited_count, count); return true; } // Push on the abandoned list. -static void mi_abandoned_push(mi_segment_t* segment) { +static void mi_abandoned_push(mi_abandoned_pool_t* pool, mi_segment_t* segment) { mi_assert_internal(segment->thread_id == 0); mi_assert_internal(mi_atomic_load_ptr_relaxed(mi_segment_t, &segment->abandoned_next) == NULL); mi_assert_internal(segment->next == NULL); mi_assert_internal(segment->used > 0); mi_tagged_segment_t next; - mi_tagged_segment_t ts = mi_atomic_load_relaxed(&abandoned); + mi_tagged_segment_t ts = mi_atomic_load_relaxed(&pool->abandoned); do { mi_atomic_store_ptr_release(mi_segment_t, &segment->abandoned_next, mi_tagged_segment_ptr(ts)); next = mi_tagged_segment(segment, ts); - } while (!mi_atomic_cas_weak_release(&abandoned, &ts, next)); - mi_atomic_increment_relaxed(&abandoned_count); + } while (!mi_atomic_cas_weak_release(&pool->abandoned, &ts, next)); + mi_atomic_increment_relaxed(&pool->abandoned_count); } // Wait until there are no more pending reads on segments that used to be in the abandoned list // called for example from `arena.c` before decommitting -void _mi_abandoned_await_readers(void) { +void _mi_abandoned_await_readers(mi_abandoned_pool_t* pool) { size_t n; do { - n = mi_atomic_load_acquire(&abandoned_readers); + n = mi_atomic_load_acquire(&pool->abandoned_readers); if (n != 0) mi_atomic_yield(); } while (n != 0); } // Pop from the abandoned list -static mi_segment_t* mi_abandoned_pop(void) { +static mi_segment_t* mi_abandoned_pop(mi_abandoned_pool_t* pool) { mi_segment_t* segment; // Check efficiently if it is empty (or if the visited list needs to be moved) - mi_tagged_segment_t ts = mi_atomic_load_relaxed(&abandoned); + mi_tagged_segment_t ts = mi_atomic_load_relaxed(&pool->abandoned); segment = mi_tagged_segment_ptr(ts); if mi_likely(segment == NULL) { - if mi_likely(!mi_abandoned_visited_revisit()) { // try to swap in the visited list on NULL + if mi_likely(!mi_abandoned_visited_revisit(pool)) { // try to swap in the visited list on NULL return NULL; } } @@ -1186,20 +1170,20 @@ static mi_segment_t* mi_abandoned_pop(void) { // a segment to be decommitted while a read is still pending, // and a tagged pointer to prevent A-B-A link corruption. // (this is called from `region.c:_mi_mem_free` for example) - mi_atomic_increment_relaxed(&abandoned_readers); // ensure no segment gets decommitted + mi_atomic_increment_relaxed(&pool->abandoned_readers); // ensure no segment gets decommitted mi_tagged_segment_t next = 0; - ts = mi_atomic_load_acquire(&abandoned); + ts = mi_atomic_load_acquire(&pool->abandoned); do { segment = mi_tagged_segment_ptr(ts); if (segment != NULL) { mi_segment_t* anext = mi_atomic_load_ptr_relaxed(mi_segment_t, &segment->abandoned_next); next = mi_tagged_segment(anext, ts); // note: reads the segment's `abandoned_next` field so should not be decommitted } - } while (segment != NULL && !mi_atomic_cas_weak_acq_rel(&abandoned, &ts, next)); - mi_atomic_decrement_relaxed(&abandoned_readers); // release reader lock + } while (segment != NULL && !mi_atomic_cas_weak_acq_rel(&pool->abandoned, &ts, next)); + mi_atomic_decrement_relaxed(&pool->abandoned_readers); // release reader lock if (segment != NULL) { mi_atomic_store_ptr_release(mi_segment_t, &segment->abandoned_next, NULL); - mi_atomic_decrement_relaxed(&abandoned_count); + mi_atomic_decrement_relaxed(&pool->abandoned_count); } return segment; } @@ -1237,7 +1221,7 @@ static void mi_segment_abandon(mi_segment_t* segment, mi_segments_tld_t* tld) { segment->thread_id = 0; mi_atomic_store_ptr_release(mi_segment_t, &segment->abandoned_next, NULL); segment->abandoned_visits = 1; // from 0 to 1 to signify it is abandoned - mi_abandoned_push(segment); + mi_abandoned_push(tld->abandoned, segment); } void _mi_segment_page_abandon(mi_page_t* page, mi_segments_tld_t* tld) { @@ -1381,7 +1365,7 @@ static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap, void _mi_abandoned_reclaim_all(mi_heap_t* heap, mi_segments_tld_t* tld) { mi_segment_t* segment; - while ((segment = mi_abandoned_pop()) != NULL) { + while ((segment = mi_abandoned_pop(tld->abandoned)) != NULL) { mi_segment_reclaim(segment, heap, 0, NULL, tld); } } @@ -1391,7 +1375,7 @@ static mi_segment_t* mi_segment_try_reclaim(mi_heap_t* heap, size_t needed_slice *reclaimed = false; mi_segment_t* segment; long max_tries = mi_option_get_clamp(mi_option_max_segment_reclaim, 8, 1024); // limit the work to bound allocation times - while ((max_tries-- > 0) && ((segment = mi_abandoned_pop()) != NULL)) { + while ((max_tries-- > 0) && ((segment = mi_abandoned_pop(tld->abandoned)) != NULL)) { segment->abandoned_visits++; // todo: an arena exclusive heap will potentially visit many abandoned unsuitable segments // and push them into the visited list and use many tries. Perhaps we can skip non-suitable ones in a better way? @@ -1418,7 +1402,7 @@ static mi_segment_t* mi_segment_try_reclaim(mi_heap_t* heap, size_t needed_slice else { // otherwise, push on the visited list so it gets not looked at too quickly again mi_segment_try_purge(segment, true /* force? */, tld->stats); // force purge if needed as we may not visit soon again - mi_abandoned_visited_push(segment); + mi_abandoned_visited_push(tld->abandoned, segment); } } return NULL; @@ -1428,11 +1412,12 @@ static mi_segment_t* mi_segment_try_reclaim(mi_heap_t* heap, size_t needed_slice void _mi_abandoned_collect(mi_heap_t* heap, bool force, mi_segments_tld_t* tld) { mi_segment_t* segment; + mi_abandoned_pool_t* pool = tld->abandoned; int max_tries = (force ? 16*1024 : 1024); // limit latency if (force) { - mi_abandoned_visited_revisit(); + mi_abandoned_visited_revisit(pool); } - while ((max_tries-- > 0) && ((segment = mi_abandoned_pop()) != NULL)) { + while ((max_tries-- > 0) && ((segment = mi_abandoned_pop(pool)) != NULL)) { mi_segment_check_free(segment,0,0,tld); // try to free up pages (due to concurrent frees) if (segment->used == 0) { // free the segment (by forced reclaim) to make it available to other threads. @@ -1444,7 +1429,7 @@ void _mi_abandoned_collect(mi_heap_t* heap, bool force, mi_segments_tld_t* tld) // otherwise, purge if needed and push on the visited list // note: forced purge can be expensive if many threads are destroyed/created as in mstress. mi_segment_try_purge(segment, force, tld->stats); - mi_abandoned_visited_push(segment); + mi_abandoned_visited_push(pool, segment); } } } diff --git a/Python/pystate.c b/Python/pystate.c index 84e2d6ea172..5f515cf475d 100644 --- a/Python/pystate.c +++ b/Python/pystate.c @@ -2533,6 +2533,11 @@ tstate_mimalloc_bind(PyThreadState *tstate) mi_tld_t *tld = &mts->tld; _mi_tld_init(tld, &mts->heaps[_Py_MIMALLOC_HEAP_MEM]); + // Exiting threads push any remaining in-use segments to the abandoned + // pool to be re-claimed later by other threads. We use per-interpreter + // pools to keep Python objects from different interpreters separate. + tld->segments.abandoned = &tstate->interp->mimalloc.abandoned_pool; + // Initialize each heap for (Py_ssize_t i = 0; i < _Py_MIMALLOC_HEAP_COUNT; i++) { _mi_heap_init_ex(&mts->heaps[i], tld, _mi_arena_id_none());