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remove segment-cache as it is superseded by better arena management

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This commit is contained in:
daanx 2023-04-13 15:37:54 -07:00
parent e6681f2d4b
commit e35e919ea4
9 changed files with 5 additions and 324 deletions
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1
CMakeLists.txt
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@ -50,7 +50,6 @@ set(mi_sources
src/page.c
src/random.c
src/segment.c
src/segment-cache.c
src/segment-map.c
src/stats.c
src/prim/prim.c)

1
ide/vs2022/mimalloc-override.vcxproj
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@ -257,7 +257,6 @@
</ClCompile>
<ClCompile Include="..\..\src\page.c" />
<ClCompile Include="..\..\src\random.c" />
<ClCompile Include="..\..\src\segment-cache.c" />
<ClCompile Include="..\..\src\segment-map.c" />
<ClCompile Include="..\..\src\segment.c" />
<ClCompile Include="..\..\src\stats.c" />

1
ide/vs2022/mimalloc.vcxproj
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@ -235,7 +235,6 @@
</ClCompile>
<ClCompile Include="..\..\src\page.c" />
<ClCompile Include="..\..\src\random.c" />
<ClCompile Include="..\..\src\segment-cache.c" />
<ClCompile Include="..\..\src\segment-map.c" />
<ClCompile Include="..\..\src\segment.c" />
<ClCompile Include="..\..\src\os.c" />

7
include/mimalloc/internal.h
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@ -120,16 +120,9 @@ void _mi_arena_free(void* p, size_t size, size_t alignment, size_t align_o
void* _mi_arena_alloc(size_t size, bool* commit, bool* large, bool* is_pinned, bool* is_zero, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld);
void* _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset, bool* commit, bool* large, bool* is_pinned, bool* is_zero, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld);
bool _mi_arena_memid_is_suitable(mi_memid_t memid, mi_arena_id_t request_arena_id);
bool _mi_arena_memid_is_os_allocated(mi_memid_t memid);
void _mi_arena_collect(bool free_arenas, bool force_decommit, mi_stats_t* stats);
bool _mi_arena_contains(const void* p);
// "segment-cache.c"
void* _mi_segment_cache_pop(size_t size, mi_commit_mask_t* commit_mask, mi_commit_mask_t* purge_mask, bool large_allowed, bool* large, bool* is_pinned, bool* is_zero, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld);
bool _mi_segment_cache_push(void* start, size_t size, mi_memid_t memid, const mi_commit_mask_t* commit_mask, const mi_commit_mask_t* purge_mask, bool is_large, bool is_pinned, mi_os_tld_t* tld);
void _mi_segment_cache_collect(bool force, mi_os_tld_t* tld);
void _mi_segment_cache_free_all(mi_os_tld_t* tld);
// "segment-map.c"
void _mi_segment_map_allocated_at(const mi_segment_t* segment);
void _mi_segment_map_freed_at(const mi_segment_t* segment);

4
src/heap.c
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@ -163,10 +163,6 @@ static void mi_heap_collect_ex(mi_heap_t* heap, mi_collect_t collect)
_mi_segment_thread_collect(&heap->tld->segments);
}
// decommit in global segment caches
// note: forced decommit can be quite expensive if many threads are created/destroyed so we do not force on abandonment
_mi_segment_cache_collect( collect == MI_FORCE, &heap->tld->os);
// collect regions on program-exit (or shared library unload)
if (force && _mi_is_main_thread() && mi_heap_is_backing(heap)) {
_mi_arena_collect(false /* destroy arenas */, true /* force purge */, &heap->tld->stats);

1
src/init.c
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@ -632,7 +632,6 @@ static void mi_cdecl mi_process_done(void) {
// or C-runtime termination code.
if (mi_option_is_enabled(mi_option_destroy_on_exit)) {
_mi_heap_destroy_all(); // forcefully release all memory held by all heaps (of this thread only!)
_mi_segment_cache_free_all(&_mi_heap_main_get()->tld->os); // release all cached segments
_mi_arena_collect(true /* destroy (owned) arenas */, true /* purge the rest */, &_mi_heap_main_get()->tld->stats);
}

277
src/segment-cache.c
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@ -1,277 +0,0 @@
/* ----------------------------------------------------------------------------
Copyright (c) 2020, Microsoft Research, Daan Leijen
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"LICENSE" at the root of this distribution.
-----------------------------------------------------------------------------*/
/* ----------------------------------------------------------------------------
Implements a cache of segments to avoid expensive OS calls and to reuse
the commit_mask to optimize the commit/decommit calls.
The full memory map of all segments is also implemented here.
-----------------------------------------------------------------------------*/
#include "mimalloc.h"
#include "mimalloc/internal.h"
#include "mimalloc/atomic.h"
#include "./bitmap.h" // atomic bitmap
// #define MI_CACHE_DISABLE 1 // define to completely disable the segment cache
#define MI_CACHE_FIELDS (16)
#define MI_CACHE_MAX (MI_BITMAP_FIELD_BITS*MI_CACHE_FIELDS) // 1024 on 64-bit
#define BITS_SET() MI_ATOMIC_VAR_INIT(UINTPTR_MAX)
#define MI_CACHE_BITS_SET MI_INIT16(BITS_SET) // note: update if MI_CACHE_FIELDS changes
typedef struct mi_cache_slot_s {
void* p;
mi_memid_t memid;
bool is_pinned;
mi_commit_mask_t commit_mask;
mi_commit_mask_t purge_mask;
_Atomic(mi_msecs_t) expire;
} mi_cache_slot_t;
static mi_decl_cache_align mi_cache_slot_t cache[MI_CACHE_MAX]; // = 0
static mi_decl_cache_align mi_bitmap_field_t cache_unavailable[MI_CACHE_FIELDS] = { MI_CACHE_BITS_SET }; // zero bit = available!
static mi_decl_cache_align mi_bitmap_field_t cache_unavailable_large[MI_CACHE_FIELDS] = { MI_CACHE_BITS_SET };
static mi_decl_cache_align mi_bitmap_field_t cache_inuse[MI_CACHE_FIELDS]; // zero bit = free
static bool mi_cdecl mi_segment_cache_is_suitable(mi_bitmap_index_t bitidx, void* arg) {
mi_arena_id_t req_arena_id = *((mi_arena_id_t*)arg);
mi_cache_slot_t* slot = &cache[mi_bitmap_index_bit(bitidx)];
return _mi_arena_memid_is_suitable(slot->memid, req_arena_id);
}
mi_decl_noinline static void* mi_segment_cache_pop_ex(
bool all_suitable,
size_t size, mi_commit_mask_t* commit_mask,
mi_commit_mask_t* purge_mask, bool large_allowed,
bool* large, bool* is_pinned, bool* is_zero,
mi_arena_id_t _req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld)
{
#ifdef MI_CACHE_DISABLE
return NULL;
#else
// only segment blocks
if (size != MI_SEGMENT_SIZE) return NULL;
// numa node determines start field
const int numa_node = _mi_os_numa_node(tld);
size_t start_field = 0;
if (numa_node > 0) {
start_field = (MI_CACHE_FIELDS / _mi_os_numa_node_count())*numa_node;
if (start_field >= MI_CACHE_FIELDS) start_field = 0;
}
// find an available slot and make it unavailable
mi_bitmap_index_t bitidx = 0;
bool claimed = false;
mi_arena_id_t req_arena_id = _req_arena_id;
mi_bitmap_pred_fun_t pred_fun = (all_suitable ? NULL : &mi_segment_cache_is_suitable); // cannot pass NULL as the arena may be exclusive itself; todo: do not put exclusive arenas in the cache?
if (large_allowed) { // large allowed?
claimed = _mi_bitmap_try_find_from_claim_pred(cache_unavailable_large, MI_CACHE_FIELDS, start_field, 1, pred_fun, &req_arena_id, &bitidx);
if (claimed) *large = true;
}
if (!claimed) {
claimed = _mi_bitmap_try_find_from_claim_pred (cache_unavailable, MI_CACHE_FIELDS, start_field, 1, pred_fun, &req_arena_id, &bitidx);
if (claimed) *large = false;
}
if (!claimed) return NULL;
// no longer available but still in-use
mi_assert_internal(_mi_bitmap_is_claimed(cache_unavailable, MI_CACHE_FIELDS, 1, bitidx));
mi_assert_internal(_mi_bitmap_is_claimed(cache_unavailable_large, MI_CACHE_FIELDS, 1, bitidx));
mi_assert_internal(_mi_bitmap_is_claimed(cache_inuse, MI_CACHE_FIELDS, 1, bitidx));
// found a slot
mi_cache_slot_t* slot = &cache[mi_bitmap_index_bit(bitidx)];
void* p = slot->p;
*memid = slot->memid;
*is_pinned = slot->is_pinned;
*is_zero = false;
*commit_mask = slot->commit_mask;
*purge_mask = slot->purge_mask;
slot->p = NULL;
mi_atomic_storei64_release(&slot->expire,(mi_msecs_t)0);
// mark the slot as free again
_mi_bitmap_unclaim(cache_inuse, MI_CACHE_FIELDS, 1, bitidx);
return p;
#endif
}
mi_decl_noinline void* _mi_segment_cache_pop(size_t size, mi_commit_mask_t* commit_mask, mi_commit_mask_t* purge_mask, bool large_allowed, bool* large, bool* is_pinned, bool* is_zero, mi_arena_id_t _req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld)
{
return mi_segment_cache_pop_ex(false, size, commit_mask, purge_mask, large_allowed, large, is_pinned, is_zero, _req_arena_id, memid, tld);
}
static mi_decl_noinline void mi_commit_mask_decommit(mi_commit_mask_t* cmask, void* p, size_t total, mi_stats_t* stats)
{
if (mi_commit_mask_is_empty(cmask)) {
// nothing
}
else if (mi_commit_mask_is_full(cmask)) {
// decommit the whole in one call
_mi_os_decommit(p, total, stats);
}
else {
// decommit parts
mi_assert_internal((total%MI_COMMIT_MASK_BITS)==0);
size_t part = total/MI_COMMIT_MASK_BITS;
size_t idx;
size_t count;
mi_commit_mask_foreach(cmask, idx, count) {
void* start = (uint8_t*)p + (idx*part);
size_t size = count*part;
_mi_os_decommit(start, size, stats);
}
mi_commit_mask_foreach_end()
}
mi_commit_mask_create_empty(cmask);
}
#define MI_MAX_PURGE_PER_PUSH (4)
static mi_decl_noinline void mi_segment_cache_purge(bool visit_all, bool force, mi_os_tld_t* tld)
{
MI_UNUSED(tld);
if (!mi_option_is_enabled(mi_option_allow_purge)) return;
mi_msecs_t now = _mi_clock_now();
size_t purged = 0;
const size_t max_visits = (visit_all ? MI_CACHE_MAX /* visit all */ : MI_CACHE_FIELDS /* probe at most N (=16) slots */);
size_t idx = (visit_all ? 0 : _mi_random_shuffle((uintptr_t)now) % MI_CACHE_MAX /* random start */ );
for (size_t visited = 0; visited < max_visits; visited++,idx++) { // visit N slots
if (idx >= MI_CACHE_MAX) idx = 0; // wrap
mi_cache_slot_t* slot = &cache[idx];
mi_msecs_t expire = mi_atomic_loadi64_relaxed(&slot->expire);
if (expire != 0 && (force || now >= expire)) { // racy read
// seems expired, first claim it from available
purged++;
mi_bitmap_index_t bitidx = mi_bitmap_index_create_from_bit(idx);
if (_mi_bitmap_claim(cache_unavailable, MI_CACHE_FIELDS, 1, bitidx, NULL)) { // no need to check large as those cannot be decommitted anyways
// it was available, we claimed it (and made it unavailable)
mi_assert_internal(_mi_bitmap_is_claimed(cache_unavailable, MI_CACHE_FIELDS, 1, bitidx));
mi_assert_internal(_mi_bitmap_is_claimed(cache_unavailable_large, MI_CACHE_FIELDS, 1, bitidx));
// we can now access it safely
expire = mi_atomic_loadi64_acquire(&slot->expire);
if (expire != 0 && (force || now >= expire)) { // safe read
mi_assert_internal(_mi_bitmap_is_claimed(cache_inuse, MI_CACHE_FIELDS, 1, bitidx));
// still expired, decommit it
mi_atomic_storei64_relaxed(&slot->expire,(mi_msecs_t)0);
mi_assert_internal(!mi_commit_mask_is_empty(&slot->commit_mask));
_mi_abandoned_await_readers(); // wait until safe to decommit
// decommit committed parts
// TODO: instead of decommit, we could also free to the OS?
mi_commit_mask_decommit(&slot->commit_mask, slot->p, MI_SEGMENT_SIZE, tld->stats);
mi_commit_mask_create_empty(&slot->purge_mask);
}
_mi_bitmap_unclaim(cache_unavailable, MI_CACHE_FIELDS, 1, bitidx); // make it available again for a pop
}
if (!visit_all && purged > MI_MAX_PURGE_PER_PUSH) break; // bound to no more than N purge tries per push
}
}
}
void _mi_segment_cache_collect(bool force, mi_os_tld_t* tld) {
if (force) {
// called on `mi_collect(true)` but not on thread termination
_mi_segment_cache_free_all(tld);
}
else {
mi_segment_cache_purge(true /* visit all */, false /* don't force unexpired */, tld);
}
}
void _mi_segment_cache_free_all(mi_os_tld_t* tld) {
mi_commit_mask_t commit_mask;
mi_commit_mask_t purge_mask;
bool is_pinned;
bool is_zero;
bool is_large;
mi_memid_t memid;
const size_t size = MI_SEGMENT_SIZE;
void* p;
do {
// keep popping and freeing the memory
p = mi_segment_cache_pop_ex(true /* all */, size, &commit_mask, &purge_mask,
true /* allow large */, &is_large, &is_pinned, &is_zero, _mi_arena_id_none(), &memid, tld);
if (p != NULL) {
size_t csize = _mi_commit_mask_committed_size(&commit_mask, size);
if (csize > 0 && !is_pinned) { _mi_stat_decrease(&_mi_stats_main.committed, csize); }
_mi_arena_free(p, size, MI_SEGMENT_ALIGN, 0, memid, is_pinned /* pretend not committed to not double count decommits */, tld->stats);
}
} while (p != NULL);
}
mi_decl_noinline bool _mi_segment_cache_push(void* start, size_t size, mi_memid_t memid, const mi_commit_mask_t* commit_mask, const mi_commit_mask_t* purge_mask, bool is_large, bool is_pinned, mi_os_tld_t* tld)
{
#ifdef MI_CACHE_DISABLE
return false;
#else
// purge expired entries
mi_segment_cache_purge(false /* limit purges to a constant N */, false /* don't force unexpired */, tld);
// only cache normal segment blocks
if (size != MI_SEGMENT_SIZE || ((uintptr_t)start % MI_SEGMENT_ALIGN) != 0) return false;
// Also do not cache arena allocated segments that cannot be decommitted. (as arena allocation is fast)
// This is a common case with reserved huge OS pages.
//
// (note: we could also allow segments that are already fully decommitted but that never happens
// as the first slice is always committed (for the segment metadata))
if (!_mi_arena_memid_is_os_allocated(memid) && is_pinned) return false;
// numa node determines start field
int numa_node = _mi_os_numa_node(NULL);
size_t start_field = 0;
if (numa_node > 0) {
start_field = (MI_CACHE_FIELDS / _mi_os_numa_node_count()) * numa_node;
if (start_field >= MI_CACHE_FIELDS) start_field = 0;
}
// find an available slot
mi_bitmap_index_t bitidx;
bool claimed = _mi_bitmap_try_find_from_claim(cache_inuse, MI_CACHE_FIELDS, start_field, 1, &bitidx);
if (!claimed) return false;
mi_assert_internal(_mi_bitmap_is_claimed(cache_unavailable, MI_CACHE_FIELDS, 1, bitidx));
mi_assert_internal(_mi_bitmap_is_claimed(cache_unavailable_large, MI_CACHE_FIELDS, 1, bitidx));
#if MI_DEBUG>1
if (is_pinned || is_large) {
mi_assert_internal(mi_commit_mask_is_full(commit_mask));
}
#endif
// set the slot
mi_cache_slot_t* slot = &cache[mi_bitmap_index_bit(bitidx)];
slot->p = start;
slot->memid = memid;
slot->is_pinned = is_pinned;
mi_atomic_storei64_relaxed(&slot->expire,(mi_msecs_t)0);
slot->commit_mask = *commit_mask;
slot->purge_mask = *purge_mask;
if (!mi_commit_mask_is_empty(commit_mask) && !is_large && !is_pinned && mi_option_is_enabled(mi_option_allow_purge)) {
long delay = mi_option_get(mi_option_purge_delay) * mi_option_get(mi_option_arena_purge_mult);
if (delay == 0) {
_mi_abandoned_await_readers(); // wait until safe to decommit
mi_commit_mask_decommit(&slot->commit_mask, start, MI_SEGMENT_SIZE, tld->stats);
mi_commit_mask_create_empty(&slot->purge_mask);
}
else {
mi_atomic_storei64_release(&slot->expire, _mi_clock_now() + delay);
}
}
// make it available
_mi_bitmap_unclaim((is_large ? cache_unavailable_large : cache_unavailable), MI_CACHE_FIELDS, 1, bitidx);
return true;
#endif
}

36
src/segment.c
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@ -11,7 +11,6 @@ terms of the MIT license. A copy of the license can be found in the file
#include <string.h> // memset
#include <stdio.h>
#define MI_USE_SEGMENT_CACHE 0
#define MI_PAGE_HUGE_ALIGN (256*1024)
static void mi_segment_try_purge(mi_segment_t* segment, bool force, mi_stats_t* stats);
@ -393,28 +392,11 @@ static void mi_segment_os_free(mi_segment_t* segment, mi_segments_tld_t* tld) {
// purge delayed decommits now? (no, leave it to the arena)
// mi_segment_try_purge(segment,true,tld->stats);
// _mi_os_free(segment, mi_segment_size(segment), /*segment->memid,*/ tld->stats);
const size_t size = mi_segment_size(segment);
#if MI_USE_SEGMENT_CACHE
if (size != MI_SEGMENT_SIZE || segment->mem_align_offset != 0 || segment->kind == MI_SEGMENT_HUGE // only push regular segments on the cache
|| !_mi_segment_cache_push(segment, size, segment->memid, &segment->commit_mask, &segment->purge_mask, segment->mem_is_large, segment->mem_is_pinned, tld->os))
#endif
{
const size_t csize = _mi_commit_mask_committed_size(&segment->commit_mask, size);
/*
// if not all committed, an arena may decommit the whole area, but that double counts
// the already decommitted parts; adjust for that in the stats.
if (!mi_commit_mask_is_full(&segment->commit_mask)) {
const size_t csize = _mi_commit_mask_committed_size(&segment->commit_mask, size);
mi_assert_internal(size > csize);
if (size > csize) {
_mi_stat_increase(&_mi_stats_main.committed, size - csize);
}
}
*/
_mi_abandoned_await_readers(); // wait until safe to free
_mi_arena_free(segment, mi_segment_size(segment), segment->mem_alignment, segment->mem_align_offset, segment->memid, csize, tld->stats);
}
const size_t csize = _mi_commit_mask_committed_size(&segment->commit_mask, size);
_mi_abandoned_await_readers(); // wait until safe to free
_mi_arena_free(segment, mi_segment_size(segment), segment->mem_alignment, segment->mem_align_offset, segment->memid, csize, tld->stats);
}
// called by threads that are terminating
@ -819,6 +801,7 @@ static mi_segment_t* mi_segment_os_alloc( size_t required, size_t page_alignment
bool* is_zero, bool* pcommit, mi_segments_tld_t* tld, mi_os_tld_t* os_tld)
{
MI_UNUSED(ppurge_mask);
mi_memid_t memid;
bool mem_large = (!eager_delayed && (MI_SECURE == 0)); // only allow large OS pages once we are no longer lazy
bool is_pinned = false;
@ -837,15 +820,6 @@ static mi_segment_t* mi_segment_os_alloc( size_t required, size_t page_alignment
}
const size_t segment_size = (*psegment_slices) * MI_SEGMENT_SLICE_SIZE;
mi_segment_t* segment = NULL;
#if MI_USE_SEGMENT_CACHE
// get from cache?
if (page_alignment == 0) {
segment = (mi_segment_t*)_mi_segment_cache_pop(segment_size, pcommit_mask, ppurge_mask, mem_large, &mem_large, &is_pinned, is_zero, req_arena_id, &memid, os_tld);
}
#else
MI_UNUSED(ppurge_mask);
#endif
// get from OS
if (segment==NULL) {

1
src/static.c
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@ -32,7 +32,6 @@ terms of the MIT license. A copy of the license can be found in the file
#include "page.c" // includes page-queue.c
#include "random.c"
#include "segment.c"
#include "segment-cache.c"
#include "segment-map.c"
#include "stats.c"
#include "prim/prim.c"