Source/bmalloc/libpas/src/libpas/pas_page_sharing_participant.h

/*
 * Copyright (c) 2019-2021 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#ifndef PAS_PAGE_SHARING_PARTICIPANT_H
#define PAS_PAGE_SHARING_PARTICIPANT_H

#include "pas_config.h"
#include "pas_lock.h"
#include "pas_page_sharing_participant_kind.h"
#include "pas_page_sharing_pool_take_result.h"
#include "pas_utils.h"

PAS_BEGIN_EXTERN_C;

struct pas_deferred_decommit_log;
struct pas_page_base;
struct pas_page_base_config;
struct pas_page_sharing_participant_opaque;
struct pas_page_sharing_participant_payload;
struct pas_page_sharing_participant_payload_with_use_epoch;
struct pas_page_sharing_pool;
typedef struct pas_deferred_decommit_log pas_deferred_decommit_log;
typedef struct pas_page_base pas_page_base;
typedef struct pas_page_base_config pas_page_base_config;
typedef struct pas_page_sharing_participant_opaque* pas_page_sharing_participant;
typedef struct pas_page_sharing_participant_payload pas_page_sharing_participant_payload;
typedef struct pas_page_sharing_participant_payload_with_use_epoch pas_page_sharing_participant_payload_with_use_epoch;
typedef struct pas_page_sharing_pool pas_page_sharing_pool;

struct pas_page_sharing_participant_payload {
    uint64_t use_epoch_for_min_heap;
    
    unsigned index_in_sharing_pool;
    unsigned index_in_sharing_pool_min_heap; /* this is a one-based index; will be zero to indicate
                                                that it's not in the pool. */
    
    /* Delta = either the use_epoch changed or a page became available.
    
       If this is false then:
       
       - use_epoch == use_epoch_for_min_heap.
       - it cannot be the case that there are empty pages but we don't belong to the min_heap.
       
       If this is true then:
       
       - we must be tracked as a delta.
    
       FIXME: There's a pretty obvious size win to be had just from removing this field. */
    bool delta_has_been_noted;
};

struct pas_page_sharing_participant_payload_with_use_epoch {
    pas_page_sharing_participant_payload base;
    
    uint64_t use_epoch;
};

#define PAS_PAGE_SHARING_PARTICIPANT_PAYLOAD_INITIALIZER \
    ((pas_page_sharing_participant_payload){ \
        .use_epoch_for_min_heap = 0, \
        .index_in_sharing_pool = 0, \
        .index_in_sharing_pool_min_heap = 0, \
        .delta_has_been_noted = false \
    })

#define PAS_PAGE_SHARING_PARTICIPANT_PAYLOAD_WITH_USE_EPOCH_INITIALIZER \
    ((pas_page_sharing_participant_payload_with_use_epoch){ \
        .base = PAS_PAGE_SHARING_PARTICIPANT_PAYLOAD_INITIALIZER, \
        .use_epoch = 0 \
    })

static inline void* pas_page_sharing_participant_get_ptr(pas_page_sharing_participant participant)
{
    return (void*)((uintptr_t)participant & ~PAS_PAGE_SHARING_PARTICIPANT_KIND_MASK);
}

static inline pas_page_sharing_participant_kind
pas_page_sharing_participant_get_kind(pas_page_sharing_participant participant)
{
    return (pas_page_sharing_participant_kind)(
        (uintptr_t)participant & PAS_PAGE_SHARING_PARTICIPANT_KIND_MASK);
}

PAS_API pas_page_sharing_participant
pas_page_sharing_participant_create(void* ptr,
                                    pas_page_sharing_participant_kind kind);

PAS_API pas_page_sharing_participant_payload*
pas_page_sharing_participant_get_payload(pas_page_sharing_participant participant);

PAS_API void pas_page_sharing_participant_payload_construct(
    pas_page_sharing_participant_payload* payload);

PAS_API void pas_page_sharing_participant_payload_with_use_epoch_construct(
    pas_page_sharing_participant_payload_with_use_epoch* payload);

PAS_API uint64_t pas_page_sharing_participant_get_use_epoch(pas_page_sharing_participant participant);

PAS_API void pas_page_sharing_participant_set_parent_pool(
    pas_page_sharing_participant participant,
    pas_page_sharing_pool* pool);

PAS_API pas_page_sharing_pool*
pas_page_sharing_participant_get_parent_pool(pas_page_sharing_participant participant);

PAS_API bool pas_page_sharing_participant_is_eligible(pas_page_sharing_participant participant);

/* This can return the following take_results:

   - none_available (note this can happen if we previously said is_eligible)
   - locks_unavailable (though not if the decommit_log is empty and we're holding no locks)
   - success */
PAS_API pas_page_sharing_pool_take_result
pas_page_sharing_participant_take_least_recently_used(
    pas_page_sharing_participant participant,
    pas_deferred_decommit_log* decommit_log,
    pas_lock_hold_mode heap_lock_hold_mode);

PAS_END_EXTERN_C;

#endif /* PAS_PAGE_SHARING_PARTICIPANT_H */