migration: refine the compression code
The current code for multi-thread compression is not clear, especially in the aspect of using lock. Refine the code to make it clear. Signed-off-by: Liang Li <liang.z.li@intel.com> Message-Id: <1462433579-13691-8-git-send-email-liang.z.li@intel.com> Signed-off-by: Amit Shah <amit.shah@redhat.com>
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@ -253,7 +253,6 @@ static struct BitmapRcu {
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} *migration_bitmap_rcu;
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struct CompressParam {
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bool start;
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bool done;
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bool quit;
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QEMUFile *file;
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@ -293,34 +292,36 @@ static QemuThread *decompress_threads;
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static QemuMutex decomp_done_lock;
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static QemuCond decomp_done_cond;
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static int do_compress_ram_page(CompressParam *param);
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static int do_compress_ram_page(QEMUFile *f, RAMBlock *block,
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ram_addr_t offset);
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static void *do_data_compress(void *opaque)
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{
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CompressParam *param = opaque;
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RAMBlock *block;
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ram_addr_t offset;
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while (!param->quit) {
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qemu_mutex_lock(¶m->mutex);
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/* Re-check the quit flag in case of
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* terminate_compression_threads is called just before
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* qemu_mutex_lock(¶m->mutex) and after
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* while(!param->quit), re-check it here can make
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* sure the compression thread terminate as expected.
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*/
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while (!param->start && !param->quit) {
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qemu_cond_wait(¶m->cond, ¶m->mutex);
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}
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if (!param->quit) {
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do_compress_ram_page(param);
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}
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param->start = false;
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while (!param->quit) {
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if (param->block) {
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block = param->block;
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offset = param->offset;
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param->block = NULL;
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qemu_mutex_unlock(¶m->mutex);
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do_compress_ram_page(param->file, block, offset);
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qemu_mutex_lock(comp_done_lock);
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param->done = true;
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qemu_cond_signal(comp_done_cond);
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qemu_mutex_unlock(comp_done_lock);
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qemu_mutex_lock(¶m->mutex);
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} else {
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qemu_cond_wait(¶m->cond, ¶m->mutex);
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}
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}
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qemu_mutex_unlock(¶m->mutex);
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return NULL;
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}
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@ -808,18 +809,15 @@ static int ram_save_page(QEMUFile *f, PageSearchStatus *pss,
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return pages;
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}
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static int do_compress_ram_page(CompressParam *param)
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static int do_compress_ram_page(QEMUFile *f, RAMBlock *block,
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ram_addr_t offset)
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{
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int bytes_sent, blen;
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uint8_t *p;
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RAMBlock *block = param->block;
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ram_addr_t offset = param->offset;
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uint8_t *p = block->host + (offset & TARGET_PAGE_MASK);
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p = block->host + (offset & TARGET_PAGE_MASK);
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bytes_sent = save_page_header(param->file, block, offset |
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bytes_sent = save_page_header(f, block, offset |
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RAM_SAVE_FLAG_COMPRESS_PAGE);
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blen = qemu_put_compression_data(param->file, p, TARGET_PAGE_SIZE,
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blen = qemu_put_compression_data(f, p, TARGET_PAGE_SIZE,
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migrate_compress_level());
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if (blen < 0) {
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bytes_sent = 0;
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@ -832,15 +830,6 @@ static int do_compress_ram_page(CompressParam *param)
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return bytes_sent;
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}
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static inline void start_compression(CompressParam *param)
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{
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param->done = false;
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qemu_mutex_lock(¶m->mutex);
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param->start = true;
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qemu_cond_signal(¶m->cond);
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qemu_mutex_unlock(¶m->mutex);
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}
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static inline void start_decompression(DecompressParam *param)
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{
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param->done = false;
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@ -860,18 +849,22 @@ static void flush_compressed_data(QEMUFile *f)
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return;
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}
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thread_count = migrate_compress_threads();
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for (idx = 0; idx < thread_count; idx++) {
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if (!comp_param[idx].done) {
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qemu_mutex_lock(comp_done_lock);
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while (!comp_param[idx].done && !comp_param[idx].quit) {
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for (idx = 0; idx < thread_count; idx++) {
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while (!comp_param[idx].done) {
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qemu_cond_wait(comp_done_cond, comp_done_lock);
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}
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qemu_mutex_unlock(comp_done_lock);
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}
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qemu_mutex_unlock(comp_done_lock);
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for (idx = 0; idx < thread_count; idx++) {
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qemu_mutex_lock(&comp_param[idx].mutex);
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if (!comp_param[idx].quit) {
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len = qemu_put_qemu_file(f, comp_param[idx].file);
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bytes_transferred += len;
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}
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qemu_mutex_unlock(&comp_param[idx].mutex);
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}
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}
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@ -893,9 +886,12 @@ static int compress_page_with_multi_thread(QEMUFile *f, RAMBlock *block,
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while (true) {
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for (idx = 0; idx < thread_count; idx++) {
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if (comp_param[idx].done) {
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comp_param[idx].done = false;
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bytes_xmit = qemu_put_qemu_file(f, comp_param[idx].file);
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qemu_mutex_lock(&comp_param[idx].mutex);
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set_compress_params(&comp_param[idx], block, offset);
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start_compression(&comp_param[idx]);
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qemu_cond_signal(&comp_param[idx].cond);
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qemu_mutex_unlock(&comp_param[idx].mutex);
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pages = 1;
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acct_info.norm_pages++;
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*bytes_transferred += bytes_xmit;
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