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migration: do not wait for free thread

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Instead of putting the main thread to sleep state to wait for
free compression thread, we can directly post it out as normal
page that reduces the latency and uses CPUs more efficiently

A parameter, compress-wait-thread, is introduced, it can be
enabled if the user really wants the old behavior

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Xiao Guangrong 2018-08-21 16:10:20 +08:00 • committed by Juan Quintela
parent 923709896b
commit 1d58872a91
5 changed files with 74 additions and 19 deletions
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45
migration/ram.c
View file

@ -1896,30 +1896,34 @@ static int compress_page_with_multi_thread(RAMState *rs, RAMBlock *block,
ram_addr_t offset)
{
int idx, thread_count, bytes_xmit = -1, pages = -1;
bool wait = migrate_compress_wait_thread();
thread_count = migrate_compress_threads();
qemu_mutex_lock(&comp_done_lock);
while (true) {
for (idx = 0; idx < thread_count; idx++) {
if (comp_param[idx].done) {
comp_param[idx].done = false;
bytes_xmit = qemu_put_qemu_file(rs->f, comp_param[idx].file);
qemu_mutex_lock(&comp_param[idx].mutex);
set_compress_params(&comp_param[idx], block, offset);
qemu_cond_signal(&comp_param[idx].cond);
qemu_mutex_unlock(&comp_param[idx].mutex);
pages = 1;
ram_counters.normal++;
ram_counters.transferred += bytes_xmit;
break;
}
}
if (pages > 0) {
retry:
for (idx = 0; idx < thread_count; idx++) {
if (comp_param[idx].done) {
comp_param[idx].done = false;
bytes_xmit = qemu_put_qemu_file(rs->f, comp_param[idx].file);
qemu_mutex_lock(&comp_param[idx].mutex);
set_compress_params(&comp_param[idx], block, offset);
qemu_cond_signal(&comp_param[idx].cond);
qemu_mutex_unlock(&comp_param[idx].mutex);
pages = 1;
ram_counters.normal++;
ram_counters.transferred += bytes_xmit;
break;
} else {
qemu_cond_wait(&comp_done_cond, &comp_done_lock);
}
}
/*
* wait for the free thread if the user specifies 'compress-wait-thread',
* otherwise we will post the page out in the main thread as normal page.
*/
if (pages < 0 && wait) {
qemu_cond_wait(&comp_done_cond, &comp_done_lock);
goto retry;
}
qemu_mutex_unlock(&comp_done_lock);
return pages;
@ -2233,7 +2237,10 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
* CPU resource.
*/
if (block == rs->last_sent_block && save_page_use_compression(rs)) {
return compress_page_with_multi_thread(rs, block, offset);
res = compress_page_with_multi_thread(rs, block, offset);
if (res > 0) {
return res;
}
} else if (migrate_use_multifd()) {
return ram_save_multifd_page(rs, block, offset);
}