Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 1 | /* |
| 2 | * QEMU generic buffers |
| 3 | * |
| 4 | * Copyright (c) 2015 Red Hat, Inc. |
| 5 | * |
| 6 | * This library is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU Lesser General Public |
| 8 | * License as published by the Free Software Foundation; either |
Chetan Pant | 61f3c91 | 2020-10-23 12:44:24 +0000 | [diff] [blame] | 9 | * version 2.1 of the License, or (at your option) any later version. |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 10 | * |
| 11 | * This library is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | * Lesser General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU Lesser General Public |
| 17 | * License along with this library; if not, see <http://www.gnu.org/licenses/>. |
| 18 | * |
| 19 | */ |
| 20 | |
Peter Maydell | aafd758 | 2016-01-29 17:49:55 +0000 | [diff] [blame] | 21 | #include "qemu/osdep.h" |
Paolo Bonzini | 87776ab | 2016-03-15 15:36:13 +0100 | [diff] [blame] | 22 | #include "qemu/host-utils.h" |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 23 | #include "qemu/buffer.h" |
Gerd Hoffmann | d2b9071 | 2015-10-30 12:10:01 +0100 | [diff] [blame] | 24 | #include "trace.h" |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 25 | |
Gerd Hoffmann | 1ff36b5 | 2015-10-30 12:10:00 +0100 | [diff] [blame] | 26 | #define BUFFER_MIN_INIT_SIZE 4096 |
| 27 | #define BUFFER_MIN_SHRINK_SIZE 65536 |
Peter Lieven | 5c10dbb | 2015-10-30 12:09:56 +0100 | [diff] [blame] | 28 | |
Wei Jiangang | d43eda3 | 2016-03-14 17:58:29 +0800 | [diff] [blame] | 29 | /* define the factor alpha for the exponential smoothing |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 30 | * that is used in the average size calculation. a shift |
| 31 | * of 7 results in an alpha of 1/2^7. */ |
| 32 | #define BUFFER_AVG_SIZE_SHIFT 7 |
| 33 | |
Peter Lieven | fd95243 | 2015-10-30 12:10:12 +0100 | [diff] [blame] | 34 | static size_t buffer_req_size(Buffer *buffer, size_t len) |
| 35 | { |
| 36 | return MAX(BUFFER_MIN_INIT_SIZE, |
| 37 | pow2ceil(buffer->offset + len)); |
| 38 | } |
| 39 | |
Peter Lieven | 4ec5ba1 | 2015-10-30 12:10:13 +0100 | [diff] [blame] | 40 | static void buffer_adj_size(Buffer *buffer, size_t len) |
| 41 | { |
| 42 | size_t old = buffer->capacity; |
| 43 | buffer->capacity = buffer_req_size(buffer, len); |
| 44 | buffer->buffer = g_realloc(buffer->buffer, buffer->capacity); |
| 45 | trace_buffer_resize(buffer->name ?: "unnamed", |
| 46 | old, buffer->capacity); |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 47 | |
| 48 | /* make it even harder for the buffer to shrink, reset average size |
Wei Jiangang | d43eda3 | 2016-03-14 17:58:29 +0800 | [diff] [blame] | 49 | * to current capacity if it is larger than the average. */ |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 50 | buffer->avg_size = MAX(buffer->avg_size, |
| 51 | buffer->capacity << BUFFER_AVG_SIZE_SHIFT); |
Peter Lieven | 4ec5ba1 | 2015-10-30 12:10:13 +0100 | [diff] [blame] | 52 | } |
Peter Lieven | fd95243 | 2015-10-30 12:10:12 +0100 | [diff] [blame] | 53 | |
Gerd Hoffmann | 810082d | 2015-10-30 12:09:57 +0100 | [diff] [blame] | 54 | void buffer_init(Buffer *buffer, const char *name, ...) |
| 55 | { |
| 56 | va_list ap; |
| 57 | |
| 58 | va_start(ap, name); |
| 59 | buffer->name = g_strdup_vprintf(name, ap); |
| 60 | va_end(ap); |
| 61 | } |
| 62 | |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 63 | static uint64_t buffer_get_avg_size(Buffer *buffer) |
| 64 | { |
| 65 | return buffer->avg_size >> BUFFER_AVG_SIZE_SHIFT; |
| 66 | } |
| 67 | |
Gerd Hoffmann | 1ff36b5 | 2015-10-30 12:10:00 +0100 | [diff] [blame] | 68 | void buffer_shrink(Buffer *buffer) |
| 69 | { |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 70 | size_t new; |
| 71 | |
| 72 | /* Calculate the average size of the buffer as |
| 73 | * avg_size = avg_size * ( 1 - a ) + required_size * a |
| 74 | * where a is 1 / 2 ^ BUFFER_AVG_SIZE_SHIFT. */ |
| 75 | buffer->avg_size *= (1 << BUFFER_AVG_SIZE_SHIFT) - 1; |
| 76 | buffer->avg_size >>= BUFFER_AVG_SIZE_SHIFT; |
| 77 | buffer->avg_size += buffer_req_size(buffer, 0); |
| 78 | |
| 79 | /* And then only shrink if the average size of the buffer is much |
| 80 | * too big, to avoid bumping up & down the buffers all the time. |
| 81 | * realloc() isn't exactly cheap ... */ |
| 82 | new = buffer_req_size(buffer, buffer_get_avg_size(buffer)); |
| 83 | if (new < buffer->capacity >> 3 && |
| 84 | new >= BUFFER_MIN_SHRINK_SIZE) { |
| 85 | buffer_adj_size(buffer, buffer_get_avg_size(buffer)); |
Gerd Hoffmann | 1ff36b5 | 2015-10-30 12:10:00 +0100 | [diff] [blame] | 86 | } |
| 87 | |
Peter Lieven | 4ec5ba1 | 2015-10-30 12:10:13 +0100 | [diff] [blame] | 88 | buffer_adj_size(buffer, 0); |
Gerd Hoffmann | 1ff36b5 | 2015-10-30 12:10:00 +0100 | [diff] [blame] | 89 | } |
| 90 | |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 91 | void buffer_reserve(Buffer *buffer, size_t len) |
| 92 | { |
| 93 | if ((buffer->capacity - buffer->offset) < len) { |
Peter Lieven | 4ec5ba1 | 2015-10-30 12:10:13 +0100 | [diff] [blame] | 94 | buffer_adj_size(buffer, len); |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 95 | } |
| 96 | } |
| 97 | |
| 98 | gboolean buffer_empty(Buffer *buffer) |
| 99 | { |
| 100 | return buffer->offset == 0; |
| 101 | } |
| 102 | |
| 103 | uint8_t *buffer_end(Buffer *buffer) |
| 104 | { |
| 105 | return buffer->buffer + buffer->offset; |
| 106 | } |
| 107 | |
| 108 | void buffer_reset(Buffer *buffer) |
| 109 | { |
| 110 | buffer->offset = 0; |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 111 | buffer_shrink(buffer); |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 112 | } |
| 113 | |
| 114 | void buffer_free(Buffer *buffer) |
| 115 | { |
Gerd Hoffmann | d2b9071 | 2015-10-30 12:10:01 +0100 | [diff] [blame] | 116 | trace_buffer_free(buffer->name ?: "unnamed", buffer->capacity); |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 117 | g_free(buffer->buffer); |
Gerd Hoffmann | 810082d | 2015-10-30 12:09:57 +0100 | [diff] [blame] | 118 | g_free(buffer->name); |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 119 | buffer->offset = 0; |
| 120 | buffer->capacity = 0; |
| 121 | buffer->buffer = NULL; |
Gerd Hoffmann | 810082d | 2015-10-30 12:09:57 +0100 | [diff] [blame] | 122 | buffer->name = NULL; |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 123 | } |
| 124 | |
| 125 | void buffer_append(Buffer *buffer, const void *data, size_t len) |
| 126 | { |
| 127 | memcpy(buffer->buffer + buffer->offset, data, len); |
| 128 | buffer->offset += len; |
| 129 | } |
| 130 | |
| 131 | void buffer_advance(Buffer *buffer, size_t len) |
| 132 | { |
| 133 | memmove(buffer->buffer, buffer->buffer + len, |
| 134 | (buffer->offset - len)); |
| 135 | buffer->offset -= len; |
Peter Lieven | f14c3d8 | 2015-10-30 12:10:14 +0100 | [diff] [blame] | 136 | buffer_shrink(buffer); |
Daniel P. Berrange | 88c5f20 | 2015-03-03 17:13:42 +0000 | [diff] [blame] | 137 | } |
Gerd Hoffmann | 4d1eb5f | 2015-10-30 12:09:58 +0100 | [diff] [blame] | 138 | |
| 139 | void buffer_move_empty(Buffer *to, Buffer *from) |
| 140 | { |
Gerd Hoffmann | d2b9071 | 2015-10-30 12:10:01 +0100 | [diff] [blame] | 141 | trace_buffer_move_empty(to->name ?: "unnamed", |
| 142 | from->offset, |
| 143 | from->name ?: "unnamed"); |
Gerd Hoffmann | 4d1eb5f | 2015-10-30 12:09:58 +0100 | [diff] [blame] | 144 | assert(to->offset == 0); |
| 145 | |
| 146 | g_free(to->buffer); |
| 147 | to->offset = from->offset; |
| 148 | to->capacity = from->capacity; |
| 149 | to->buffer = from->buffer; |
| 150 | |
| 151 | from->offset = 0; |
| 152 | from->capacity = 0; |
| 153 | from->buffer = NULL; |
| 154 | } |
Gerd Hoffmann | 830a958 | 2015-10-30 12:09:59 +0100 | [diff] [blame] | 155 | |
| 156 | void buffer_move(Buffer *to, Buffer *from) |
| 157 | { |
| 158 | if (to->offset == 0) { |
| 159 | buffer_move_empty(to, from); |
| 160 | return; |
| 161 | } |
| 162 | |
Gerd Hoffmann | d2b9071 | 2015-10-30 12:10:01 +0100 | [diff] [blame] | 163 | trace_buffer_move(to->name ?: "unnamed", |
| 164 | from->offset, |
| 165 | from->name ?: "unnamed"); |
Gerd Hoffmann | 830a958 | 2015-10-30 12:09:59 +0100 | [diff] [blame] | 166 | buffer_reserve(to, from->offset); |
| 167 | buffer_append(to, from->buffer, from->offset); |
| 168 | |
| 169 | g_free(from->buffer); |
| 170 | from->offset = 0; |
| 171 | from->capacity = 0; |
| 172 | from->buffer = NULL; |
| 173 | } |