On 07/23/2018 11:25 AM, Peter Xu wrote:
On Thu, Jul 19, 2018 at 08:15:13PM +0800, guangrong.xiao@xxxxxxxxx wrote:@@ -3113,6 +3132,8 @@ static Property migration_properties[] = { DEFINE_PROP_UINT8("x-compress-threads", MigrationState, parameters.compress_threads, DEFAULT_MIGRATE_COMPRESS_THREAD_COUNT), + DEFINE_PROP_BOOL("x-compress-wait-thread", MigrationState, + parameters.compress_wait_thread, false),This performance feature bit makes sense to me, but I would still think it should be true by default to keep the old behavior: - it might change the behavior drastically: we might be in a state between "normal" migration and "compressed" migration since we'll contain both of the pages. Old compression users might not expect that. - it might still even perform worse - an extreme case is that when network bandwidth is very very limited but instead we have plenty of CPU resources. [1] So it's really a good tunable for me when people really needs to understand what's it before turning it on.
That looks good to me.
DEFINE_PROP_UINT8("x-decompress-threads", MigrationState, parameters.decompress_threads, DEFAULT_MIGRATE_DECOMPRESS_THREAD_COUNT), diff --git a/migration/migration.h b/migration/migration.h index 64a7b33735..a46b9e6c8d 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -271,6 +271,7 @@ bool migrate_use_return_path(void); bool migrate_use_compression(void); int migrate_compress_level(void); int migrate_compress_threads(void); +int migrate_compress_wait_thread(void); int migrate_decompress_threads(void); bool migrate_use_events(void); bool migrate_postcopy_blocktime(void); diff --git a/migration/ram.c b/migration/ram.c index 52dd678092..0ad234c692 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1889,30 +1889,34 @@ 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); } } + + /* + * if there is no thread is free to compress the data and the user + * really expects the slowdown, wait it.Considering [1] above, IMHO it might not really be a slow down but it depends. Maybe only mentioning about the fact that we're sending a normal page instead of the compressed page if wait is not specified.
Okay, will update the comments based on your suggestion.
+ */ + if (pages < 0 && wait) { + qemu_cond_wait(&comp_done_cond, &comp_done_lock); + goto retry; + } qemu_mutex_unlock(&comp_done_lock);return pages;@@ -2226,7 +2230,10 @@ 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); } diff --git a/qapi/migration.json b/qapi/migration.json index 186e8a7303..b4f394844b 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -462,6 +462,11 @@ # @compress-threads: Set compression thread count to be used in live migration, # the compression thread count is an integer between 1 and 255. # +# @compress-wait-thread: Wait if no thread is free to compress the memory page +# if it's enabled, otherwise, the page will be posted out immediately +# in the main thread without compression. It's off on default. +# (Since: 3.0) +#Should "Since 3.1" in all the places.
Oh... the thing goes faster than i realized :)
We'll need to touch up the "by default" part depending on whether we'd need to change it according to above comment. Otherwise it looks good to me.
Okay, thank you, Peter.
