diff options
author | José Pekkarinen <jose.pekkarinen@nokia.com> | 2016-05-18 13:18:31 +0300 |
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committer | José Pekkarinen <jose.pekkarinen@nokia.com> | 2016-05-18 13:42:15 +0300 |
commit | 437fd90c0250dee670290f9b714253671a990160 (patch) | |
tree | b871786c360704244a07411c69fb58da9ead4a06 /qemu/util/buffer.c | |
parent | 5bbd6fe9b8bab2a93e548c5a53b032d1939eec05 (diff) |
These changes are the raw update to qemu-2.6.
Collission happened in the following patches:
migration: do cleanup operation after completion(738df5b9)
Bug fix.(1750c932f86)
kvmclock: add a new function to update env->tsc.(b52baab2)
The code provided by the patches was already in the upstreamed
version.
Change-Id: I3cc11841a6a76ae20887b2e245710199e1ea7f9a
Signed-off-by: José Pekkarinen <jose.pekkarinen@nokia.com>
Diffstat (limited to 'qemu/util/buffer.c')
-rw-r--r-- | qemu/util/buffer.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/qemu/util/buffer.c b/qemu/util/buffer.c new file mode 100644 index 000000000..a6118bf5b --- /dev/null +++ b/qemu/util/buffer.c @@ -0,0 +1,172 @@ +/* + * QEMU generic buffers + * + * Copyright (c) 2015 Red Hat, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, see <http://www.gnu.org/licenses/>. + * + */ + +#include "qemu/osdep.h" +#include "qemu/buffer.h" +#include "trace.h" + +#define BUFFER_MIN_INIT_SIZE 4096 +#define BUFFER_MIN_SHRINK_SIZE 65536 + +/* define the factor alpha for the expentional smoothing + * that is used in the average size calculation. a shift + * of 7 results in an alpha of 1/2^7. */ +#define BUFFER_AVG_SIZE_SHIFT 7 + +static size_t buffer_req_size(Buffer *buffer, size_t len) +{ + return MAX(BUFFER_MIN_INIT_SIZE, + pow2ceil(buffer->offset + len)); +} + +static void buffer_adj_size(Buffer *buffer, size_t len) +{ + size_t old = buffer->capacity; + buffer->capacity = buffer_req_size(buffer, len); + buffer->buffer = g_realloc(buffer->buffer, buffer->capacity); + trace_buffer_resize(buffer->name ?: "unnamed", + old, buffer->capacity); + + /* make it even harder for the buffer to shrink, reset average size + * to currenty capacity if it is larger than the average. */ + buffer->avg_size = MAX(buffer->avg_size, + buffer->capacity << BUFFER_AVG_SIZE_SHIFT); +} + +void buffer_init(Buffer *buffer, const char *name, ...) +{ + va_list ap; + + va_start(ap, name); + buffer->name = g_strdup_vprintf(name, ap); + va_end(ap); +} + +static uint64_t buffer_get_avg_size(Buffer *buffer) +{ + return buffer->avg_size >> BUFFER_AVG_SIZE_SHIFT; +} + +void buffer_shrink(Buffer *buffer) +{ + size_t new; + + /* Calculate the average size of the buffer as + * avg_size = avg_size * ( 1 - a ) + required_size * a + * where a is 1 / 2 ^ BUFFER_AVG_SIZE_SHIFT. */ + buffer->avg_size *= (1 << BUFFER_AVG_SIZE_SHIFT) - 1; + buffer->avg_size >>= BUFFER_AVG_SIZE_SHIFT; + buffer->avg_size += buffer_req_size(buffer, 0); + + /* And then only shrink if the average size of the buffer is much + * too big, to avoid bumping up & down the buffers all the time. + * realloc() isn't exactly cheap ... */ + new = buffer_req_size(buffer, buffer_get_avg_size(buffer)); + if (new < buffer->capacity >> 3 && + new >= BUFFER_MIN_SHRINK_SIZE) { + buffer_adj_size(buffer, buffer_get_avg_size(buffer)); + } + + buffer_adj_size(buffer, 0); +} + +void buffer_reserve(Buffer *buffer, size_t len) +{ + if ((buffer->capacity - buffer->offset) < len) { + buffer_adj_size(buffer, len); + } +} + +gboolean buffer_empty(Buffer *buffer) +{ + return buffer->offset == 0; +} + +uint8_t *buffer_end(Buffer *buffer) +{ + return buffer->buffer + buffer->offset; +} + +void buffer_reset(Buffer *buffer) +{ + buffer->offset = 0; + buffer_shrink(buffer); +} + +void buffer_free(Buffer *buffer) +{ + trace_buffer_free(buffer->name ?: "unnamed", buffer->capacity); + g_free(buffer->buffer); + g_free(buffer->name); + buffer->offset = 0; + buffer->capacity = 0; + buffer->buffer = NULL; + buffer->name = NULL; +} + +void buffer_append(Buffer *buffer, const void *data, size_t len) +{ + memcpy(buffer->buffer + buffer->offset, data, len); + buffer->offset += len; +} + +void buffer_advance(Buffer *buffer, size_t len) +{ + memmove(buffer->buffer, buffer->buffer + len, + (buffer->offset - len)); + buffer->offset -= len; + buffer_shrink(buffer); +} + +void buffer_move_empty(Buffer *to, Buffer *from) +{ + trace_buffer_move_empty(to->name ?: "unnamed", + from->offset, + from->name ?: "unnamed"); + assert(to->offset == 0); + + g_free(to->buffer); + to->offset = from->offset; + to->capacity = from->capacity; + to->buffer = from->buffer; + + from->offset = 0; + from->capacity = 0; + from->buffer = NULL; +} + +void buffer_move(Buffer *to, Buffer *from) +{ + if (to->offset == 0) { + buffer_move_empty(to, from); + return; + } + + trace_buffer_move(to->name ?: "unnamed", + from->offset, + from->name ?: "unnamed"); + buffer_reserve(to, from->offset); + buffer_append(to, from->buffer, from->offset); + + g_free(from->buffer); + from->offset = 0; + from->capacity = 0; + from->buffer = NULL; +} |