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/*
*
* Copyright 2017 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include <grpc/support/port_platform.h>
#include "src/core/lib/gpr/arena.h"
#include <string.h>
#include <grpc/support/alloc.h>
#include <grpc/support/atm.h>
#include <grpc/support/log.h>
#include <grpc/support/sync.h>
#include "src/core/lib/gpr/alloc.h"
// Uncomment this to use a simple arena that simply allocates the
// requested amount of memory for each call to gpr_arena_alloc(). This
// effectively eliminates the efficiency gain of using an arena, but it
// may be useful for debugging purposes.
//#define SIMPLE_ARENA_FOR_DEBUGGING
#ifdef SIMPLE_ARENA_FOR_DEBUGGING
struct gpr_arena {
gpr_mu mu;
void** ptrs;
size_t num_ptrs;
};
gpr_arena* gpr_arena_create(size_t ignored_initial_size) {
gpr_arena* arena = (gpr_arena*)gpr_zalloc(sizeof(*arena));
gpr_mu_init(&arena->mu);
return arena;
}
size_t gpr_arena_destroy(gpr_arena* arena) {
gpr_mu_destroy(&arena->mu);
for (size_t i = 0; i < arena->num_ptrs; ++i) {
gpr_free(arena->ptrs[i]);
}
gpr_free(arena->ptrs);
gpr_free(arena);
return 1; // Value doesn't matter, since it won't be used.
}
void* gpr_arena_alloc(gpr_arena* arena, size_t size) {
gpr_mu_lock(&arena->mu);
arena->ptrs =
(void**)gpr_realloc(arena->ptrs, sizeof(void*) * (arena->num_ptrs + 1));
void* retval = arena->ptrs[arena->num_ptrs++] = gpr_zalloc(size);
gpr_mu_unlock(&arena->mu);
return retval;
}
#else // SIMPLE_ARENA_FOR_DEBUGGING
// TODO(roth): We currently assume that all callers need alignment of 16
// bytes, which may be wrong in some cases. As part of converting the
// arena API to C++, we should consider replacing gpr_arena_alloc() with a
// template that takes the type of the value being allocated, which
// would allow us to use the alignment actually needed by the caller.
typedef struct zone {
size_t size_begin; // All the space we have set aside for allocations up
// until this zone.
size_t size_end; // size_end = size_begin plus all the space we set aside for
// allocations in zone z itself.
zone* next;
} zone;
struct gpr_arena {
gpr_atm size_so_far;
zone initial_zone;
gpr_mu arena_growth_mutex;
};
static void* zalloc_aligned(size_t size) {
void* ptr = gpr_malloc_aligned(size, GPR_MAX_ALIGNMENT);
memset(ptr, 0, size);
return ptr;
}
gpr_arena* gpr_arena_create(size_t initial_size) {
initial_size = GPR_ROUND_UP_TO_ALIGNMENT_SIZE(initial_size);
gpr_arena* a = static_cast<gpr_arena*>(zalloc_aligned(
GPR_ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(gpr_arena)) + initial_size));
a->initial_zone.size_end = initial_size;
gpr_mu_init(&a->arena_growth_mutex);
return a;
}
size_t gpr_arena_destroy(gpr_arena* arena) {
gpr_mu_destroy(&arena->arena_growth_mutex);
gpr_atm size = gpr_atm_no_barrier_load(&arena->size_so_far);
zone* z = arena->initial_zone.next;
gpr_free_aligned(arena);
while (z) {
zone* next_z = z->next;
gpr_free_aligned(z);
z = next_z;
}
return static_cast<size_t>(size);
}
void* gpr_arena_alloc(gpr_arena* arena, size_t size) {
size = GPR_ROUND_UP_TO_ALIGNMENT_SIZE(size);
size_t previous_size_of_arena_allocations = static_cast<size_t>(
gpr_atm_no_barrier_fetch_add(&arena->size_so_far, size));
size_t updated_size_of_arena_allocations =
previous_size_of_arena_allocations + size;
zone* z = &arena->initial_zone;
// Check to see if the allocation isn't able to end in the initial zone.
// This statement is true only in the uncommon case because of our arena
// sizing historesis (that is, most calls should have a large enough initial
// zone and will not need to grow the arena).
if (updated_size_of_arena_allocations > z->size_end) {
// Find a zone to fit this allocation
gpr_mu_lock(&arena->arena_growth_mutex);
while (updated_size_of_arena_allocations > z->size_end) {
if (z->next == nullptr) {
// Note that we do an extra increment of size_so_far to prevent multiple
// simultaneous callers from stepping on each other. However, this extra
// increment means some space in the arena is wasted.
// So whenever we need to allocate x bytes and there are x - n (where
// n > 0) remaining in the current zone, we will waste x bytes (x - n
// in the current zone and n in the new zone).
previous_size_of_arena_allocations = static_cast<size_t>(
gpr_atm_no_barrier_fetch_add(&arena->size_so_far, size));
updated_size_of_arena_allocations =
previous_size_of_arena_allocations + size;
size_t next_z_size = updated_size_of_arena_allocations;
z->next = static_cast<zone*>(zalloc_aligned(
GPR_ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(zone)) + next_z_size));
z->next->size_begin = z->size_end;
z->next->size_end = z->size_end + next_z_size;
}
z = z->next;
}
gpr_mu_unlock(&arena->arena_growth_mutex);
}
GPR_ASSERT(previous_size_of_arena_allocations >= z->size_begin);
GPR_ASSERT(updated_size_of_arena_allocations <= z->size_end);
// Skip the first part of the zone, which just contains tracking information.
// For the initial zone, this is the gpr_arena struct and for any other zone,
// it's the zone struct.
char* start_of_allocation_space =
(z == &arena->initial_zone)
? reinterpret_cast<char*>(arena) +
GPR_ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(gpr_arena))
: reinterpret_cast<char*>(z) +
GPR_ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(zone));
// previous_size_of_arena_allocations - size_begin is how many bytes have been
// allocated into the current zone
return start_of_allocation_space + previous_size_of_arena_allocations -
z->size_begin;
}
#endif // SIMPLE_ARENA_FOR_DEBUGGING
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