2 * Copyright (c) Meta Platforms, Inc. and affiliates.
5 * This source code is licensed under both the BSD-style license (found in the
6 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
7 * in the COPYING file in the root directory of this source tree).
8 * You may select, at your option, one of the above-listed licenses.
12 * FileIO AsyncIO exposes read/write IO pools that allow doing IO asynchronously.
13 * Current implementation relies on having one thread that reads and one that
15 * Each IO pool supports up to `MAX_IO_JOBS` that can be enqueued for work, but
16 * are performed serially by the appropriate worker thread.
17 * Most systems exposes better primitives to perform asynchronous IO, such as
18 * io_uring on newer linux systems. The API is built in such a way that in the
19 * future we could replace the threads with better solutions when available.
22 #ifndef ZSTD_FILEIO_ASYNCIO_H
23 #define ZSTD_FILEIO_ASYNCIO_H
25 #if defined (__cplusplus)
29 #include "../lib/common/mem.h" /* U32, U64 */
30 #include "fileio_types.h"
33 #include "../lib/common/pool.h"
34 #include "../lib/common/threading.h"
36 #define MAX_IO_JOBS (10)
39 /* These struct fields should be set only on creation and not changed afterwards */
43 const FIO_prefs_t* prefs;
44 POOL_function poolFunction;
46 /* Controls the file we currently write to, make changes only by using provided utility functions */
49 /* The jobs and availableJobsCount fields are accessed by both the main and worker threads and should
50 * only be mutated after locking the mutex */
51 ZSTD_pthread_mutex_t ioJobsMutex;
52 void* availableJobs[MAX_IO_JOBS];
53 int availableJobsCount;
60 /* State regarding the currently read file */
65 /* We may hold an IOJob object as needed if we actively expose its buffer. */
68 /* Coalesce buffer is used to join two buffers in case where we need to read more bytes than left in
69 * the first of them. Shouldn't be accessed from outside ot utility functions. */
72 /* Read buffer can be used by consumer code, take care when copying this pointer aside as it might
73 * change when consuming / refilling buffer. */
75 size_t srcBufferLoaded;
77 /* We need to know what tasks completed so we can use their buffers when their time comes.
78 * Should only be accessed after locking base.ioJobsMutex . */
79 void* completedJobs[MAX_IO_JOBS];
80 int completedJobsCount;
81 ZSTD_pthread_cond_t jobCompletedCond;
90 /* These fields are automatically set and shouldn't be changed by non WritePool code. */
96 /* This field should be changed before a job is queued for execution and should contain the number
97 * of bytes to write from the buffer. */
98 size_t usedBufferSize;
103 * Returns 1 if AsyncIO is supported on the system, 0 otherwise. */
104 int AIO_supported(void);
107 /* AIO_WritePool_releaseIoJob:
108 * Releases an acquired job back to the pool. Doesn't execute the job. */
109 void AIO_WritePool_releaseIoJob(IOJob_t *job);
111 /* AIO_WritePool_acquireJob:
112 * Returns an available write job to be used for a future write. */
113 IOJob_t* AIO_WritePool_acquireJob(WritePoolCtx_t *ctx);
115 /* AIO_WritePool_enqueueAndReacquireWriteJob:
116 * Enqueues a write job for execution and acquires a new one.
117 * After execution `job`'s pointed value would change to the newly acquired job.
118 * Make sure to set `usedBufferSize` to the wanted length before call.
119 * The queued job shouldn't be used directly after queueing it. */
120 void AIO_WritePool_enqueueAndReacquireWriteJob(IOJob_t **job);
122 /* AIO_WritePool_sparseWriteEnd:
123 * Ends sparse writes to the current file.
124 * Blocks on completion of all current write jobs before executing. */
125 void AIO_WritePool_sparseWriteEnd(WritePoolCtx_t *ctx);
127 /* AIO_WritePool_setFile:
128 * Sets the destination file for future writes in the pool.
129 * Requires completion of all queues write jobs and release of all otherwise acquired jobs.
130 * Also requires ending of sparse write if a previous file was used in sparse mode. */
131 void AIO_WritePool_setFile(WritePoolCtx_t *ctx, FILE* file);
133 /* AIO_WritePool_getFile:
134 * Returns the file the writePool is currently set to write to. */
135 FILE* AIO_WritePool_getFile(const WritePoolCtx_t* ctx);
137 /* AIO_WritePool_closeFile:
138 * Ends sparse write and closes the writePool's current file and sets the file to NULL.
139 * Requires completion of all queues write jobs and release of all otherwise acquired jobs. */
140 int AIO_WritePool_closeFile(WritePoolCtx_t *ctx);
142 /* AIO_WritePool_create:
143 * Allocates and sets and a new write pool including its included jobs.
144 * bufferSize should be set to the maximal buffer we want to write to at a time. */
145 WritePoolCtx_t* AIO_WritePool_create(const FIO_prefs_t* prefs, size_t bufferSize);
147 /* AIO_WritePool_free:
148 * Frees and releases a writePool and its resources. Closes destination file. */
149 void AIO_WritePool_free(WritePoolCtx_t* ctx);
151 /* AIO_WritePool_setAsync:
152 * Allows (de)activating async mode, to be used when the expected overhead
153 * of asyncio costs more than the expected gains. */
154 void AIO_WritePool_setAsync(WritePoolCtx_t* ctx, int async);
156 /* AIO_ReadPool_create:
157 * Allocates and sets and a new readPool including its included jobs.
158 * bufferSize should be set to the maximal buffer we want to read at a time, will also be used
159 * as our basic read size. */
160 ReadPoolCtx_t* AIO_ReadPool_create(const FIO_prefs_t* prefs, size_t bufferSize);
162 /* AIO_ReadPool_free:
163 * Frees and releases a readPool and its resources. Closes source file. */
164 void AIO_ReadPool_free(ReadPoolCtx_t* ctx);
166 /* AIO_ReadPool_setAsync:
167 * Allows (de)activating async mode, to be used when the expected overhead
168 * of asyncio costs more than the expected gains. */
169 void AIO_ReadPool_setAsync(ReadPoolCtx_t* ctx, int async);
171 /* AIO_ReadPool_consumeBytes:
172 * Consumes byes from srcBuffer's beginning and updates srcBufferLoaded accordingly. */
173 void AIO_ReadPool_consumeBytes(ReadPoolCtx_t *ctx, size_t n);
175 /* AIO_ReadPool_fillBuffer:
176 * Makes sure buffer has at least n bytes loaded (as long as n is not bigger than the initialized bufferSize).
177 * Returns if srcBuffer has at least n bytes loaded or if we've reached the end of the file.
178 * Return value is the number of bytes added to the buffer.
179 * Note that srcBuffer might have up to 2 times bufferSize bytes. */
180 size_t AIO_ReadPool_fillBuffer(ReadPoolCtx_t *ctx, size_t n);
182 /* AIO_ReadPool_consumeAndRefill:
183 * Consumes the current buffer and refills it with bufferSize bytes. */
184 size_t AIO_ReadPool_consumeAndRefill(ReadPoolCtx_t *ctx);
186 /* AIO_ReadPool_setFile:
187 * Sets the source file for future read in the pool. Initiates reading immediately if file is not NULL.
188 * Waits for all current enqueued tasks to complete if a previous file was set. */
189 void AIO_ReadPool_setFile(ReadPoolCtx_t *ctx, FILE* file);
191 /* AIO_ReadPool_getFile:
192 * Returns the current file set for the read pool. */
193 FILE* AIO_ReadPool_getFile(const ReadPoolCtx_t *ctx);
195 /* AIO_ReadPool_closeFile:
196 * Closes the current set file. Waits for all current enqueued tasks to complete and resets state. */
197 int AIO_ReadPool_closeFile(ReadPoolCtx_t *ctx);
199 #if defined (__cplusplus)
203 #endif /* ZSTD_FILEIO_ASYNCIO_H */