* Paolo Bonzini (pbonzini@xxxxxxxxxx) wrote:
> On 23/11/18 19:17, Dr. David Alan Gilbert wrote:
> > * guangrong.xiao@xxxxxxxxx (guangrong.xiao@xxxxxxxxx) wrote:
> >> From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxx>
> >>
> >> Adapt the compression code to the threaded workqueue
> >>
> >> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxx>
> >> ---
> >> migration/ram.c | 308 ++++++++++++++++++++------------------------------------
> >> 1 file changed, 110 insertions(+), 198 deletions(-)
> >>
> >> diff --git a/migration/ram.c b/migration/ram.c
> >> index 7e7deec4d8..254c08f27b 100644
> >> --- a/migration/ram.c
> >> +++ b/migration/ram.c
> >> @@ -57,6 +57,7 @@
> >> #include "qemu/uuid.h"
> >> #include "savevm.h"
> >> #include "qemu/iov.h"
> >> +#include "qemu/threaded-workqueue.h"
> >>
> >> /***********************************************************/
> >> /* ram save/restore */
> >> @@ -349,22 +350,6 @@ typedef struct PageSearchStatus PageSearchStatus;
> >>
> >> CompressionStats compression_counters;
> >>
> >> -struct CompressParam {
> >> - bool done;
> >> - bool quit;
> >> - bool zero_page;
> >> - QEMUFile *file;
> >> - QemuMutex mutex;
> >> - QemuCond cond;
> >> - RAMBlock *block;
> >> - ram_addr_t offset;
> >> -
> >> - /* internally used fields */
> >> - z_stream stream;
> >> - uint8_t *originbuf;
> >> -};
> >> -typedef struct CompressParam CompressParam;
> >> -
> >> struct DecompressParam {
> >> bool done;
> >> bool quit;
> >> @@ -377,15 +362,6 @@ struct DecompressParam {
> >> };
> >> typedef struct DecompressParam DecompressParam;
> >>
> >> -static CompressParam *comp_param;
> >> -static QemuThread *compress_threads;
> >> -/* comp_done_cond is used to wake up the migration thread when
> >> - * one of the compression threads has finished the compression.
> >> - * comp_done_lock is used to co-work with comp_done_cond.
> >> - */
> >> -static QemuMutex comp_done_lock;
> >> -static QemuCond comp_done_cond;
> >> -/* The empty QEMUFileOps will be used by file in CompressParam */
> >> static const QEMUFileOps empty_ops = { };
> >>
> >> static QEMUFile *decomp_file;
> >> @@ -394,125 +370,6 @@ static QemuThread *decompress_threads;
> >> static QemuMutex decomp_done_lock;
> >> static QemuCond decomp_done_cond;
> >>
> >> -static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
> >> - ram_addr_t offset, uint8_t *source_buf);
> >> -
> >> -static void *do_data_compress(void *opaque)
> >> -{
> >> - CompressParam *param = opaque;
> >> - RAMBlock *block;
> >> - ram_addr_t offset;
> >> - bool zero_page;
> >> -
> >> - qemu_mutex_lock(¶m->mutex);
> >> - while (!param->quit) {
> >> - if (param->block) {
> >> - block = param->block;
> >> - offset = param->offset;
> >> - param->block = NULL;
> >> - qemu_mutex_unlock(¶m->mutex);
> >> -
> >> - zero_page = do_compress_ram_page(param->file, ¶m->stream,
> >> - block, offset, param->originbuf);
> >> -
> >> - qemu_mutex_lock(&comp_done_lock);
> >> - param->done = true;
> >> - param->zero_page = zero_page;
> >> - qemu_cond_signal(&comp_done_cond);
> >> - qemu_mutex_unlock(&comp_done_lock);
> >> -
> >> - qemu_mutex_lock(¶m->mutex);
> >> - } else {
> >> - qemu_cond_wait(¶m->cond, ¶m->mutex);
> >> - }
> >> - }
> >> - qemu_mutex_unlock(¶m->mutex);
> >> -
> >> - return NULL;
> >> -}
> >> -
> >> -static void compress_threads_save_cleanup(void)
> >> -{
> >> - int i, thread_count;
> >> -
> >> - if (!migrate_use_compression() || !comp_param) {
> >> - return;
> >> - }
> >> -
> >> - thread_count = migrate_compress_threads();
> >> - for (i = 0; i < thread_count; i++) {
> >> - /*
> >> - * we use it as a indicator which shows if the thread is
> >> - * properly init'd or not
> >> - */
> >> - if (!comp_param[i].file) {
> >> - break;
> >> - }
> >> -
> >> - qemu_mutex_lock(&comp_param[i].mutex);
> >> - comp_param[i].quit = true;
> >> - qemu_cond_signal(&comp_param[i].cond);
> >> - qemu_mutex_unlock(&comp_param[i].mutex);
> >> -
> >> - qemu_thread_join(compress_threads + i);
> >> - qemu_mutex_destroy(&comp_param[i].mutex);
> >> - qemu_cond_destroy(&comp_param[i].cond);
> >> - deflateEnd(&comp_param[i].stream);
> >> - g_free(comp_param[i].originbuf);
> >> - qemu_fclose(comp_param[i].file);
> >> - comp_param[i].file = NULL;
> >> - }
> >> - qemu_mutex_destroy(&comp_done_lock);
> >> - qemu_cond_destroy(&comp_done_cond);
> >> - g_free(compress_threads);
> >> - g_free(comp_param);
> >> - compress_threads = NULL;
> >> - comp_param = NULL;
> >> -}
> >> -
> >> -static int compress_threads_save_setup(void)
> >> -{
> >> - int i, thread_count;
> >> -
> >> - if (!migrate_use_compression()) {
> >> - return 0;
> >> - }
> >> - thread_count = migrate_compress_threads();
> >> - compress_threads = g_new0(QemuThread, thread_count);
> >> - comp_param = g_new0(CompressParam, thread_count);
> >> - qemu_cond_init(&comp_done_cond);
> >> - qemu_mutex_init(&comp_done_lock);
> >> - for (i = 0; i < thread_count; i++) {
> >> - comp_param[i].originbuf = g_try_malloc(TARGET_PAGE_SIZE);
> >> - if (!comp_param[i].originbuf) {
> >> - goto exit;
> >> - }
> >> -
> >> - if (deflateInit(&comp_param[i].stream,
> >> - migrate_compress_level()) != Z_OK) {
> >> - g_free(comp_param[i].originbuf);
> >> - goto exit;
> >> - }
> >> -
> >> - /* comp_param[i].file is just used as a dummy buffer to save data,
> >> - * set its ops to empty.
> >> - */
> >> - comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops);
> >> - comp_param[i].done = true;
> >> - comp_param[i].quit = false;
> >> - qemu_mutex_init(&comp_param[i].mutex);
> >> - qemu_cond_init(&comp_param[i].cond);
> >> - qemu_thread_create(compress_threads + i, "compress",
> >> - do_data_compress, comp_param + i,
> >> - QEMU_THREAD_JOINABLE);
> >> - }
> >> - return 0;
> >> -
> >> -exit:
> >> - compress_threads_save_cleanup();
> >> - return -1;
> >> -}
> >> -
> >> /* Multiple fd's */
> >>
> >> #define MULTIFD_MAGIC 0x11223344U
> >> @@ -1909,12 +1766,25 @@ exit:
> >> return zero_page;
> >> }
> >>
> >> +struct CompressData {
> >> + /* filled by migration thread.*/
> >> + RAMBlock *block;
> >> + ram_addr_t offset;
> >> +
> >> + /* filled by compress thread. */
> >> + QEMUFile *file;
> >> + z_stream stream;
> >> + uint8_t *originbuf;
> >> + bool zero_page;
> >> +};
> >> +typedef struct CompressData CompressData;
> >> +
> >> static void
> >> -update_compress_thread_counts(const CompressParam *param, int bytes_xmit)
> >> +update_compress_thread_counts(CompressData *cd, int bytes_xmit)
> >
> > Keep the const?
> >> {
> >> ram_counters.transferred += bytes_xmit;
> >>
> >> - if (param->zero_page) {
> >> + if (cd->zero_page) {
> >> ram_counters.duplicate++;
> >> return;
> >> }
> >> @@ -1924,81 +1794,123 @@ update_compress_thread_counts(const CompressParam *param, int bytes_xmit)
> >> compression_counters.pages++;
> >> }
> >>
> >> +static int compress_thread_data_init(void *request)
> >> +{
> >> + CompressData *cd = request;
> >> +
> >> + cd->originbuf = g_try_malloc(TARGET_PAGE_SIZE);
> >> + if (!cd->originbuf) {
> >> + return -1;
> >> + }
> >> +
> >> + if (deflateInit(&cd->stream, migrate_compress_level()) != Z_OK) {
> >> + g_free(cd->originbuf);
> >> + return -1;
> >> + }
> >
> > Please print errors if you fail in any case so we can easily tell what
> > happened.
> >
> >> + cd->file = qemu_fopen_ops(NULL, &empty_ops);
> >> + return 0;
> >> +}
> >> +
> >> +static void compress_thread_data_fini(void *request)
> >> +{
> >> + CompressData *cd = request;
> >> +
> >> + qemu_fclose(cd->file);
> >> + deflateEnd(&cd->stream);
> >> + g_free(cd->originbuf);
> >> +}
> >> +
> >> +static void compress_thread_data_handler(void *request)
> >> +{
> >> + CompressData *cd = request;
> >> +
> >> + /*
> >> + * if compression fails, it will be indicated by
> >> + * migrate_get_current()->to_dst_file.
> >> + */
> >> + cd->zero_page = do_compress_ram_page(cd->file, &cd->stream, cd->block,
> >> + cd->offset, cd->originbuf);
> >> +}
> >> +
> >> +static void compress_thread_data_done(void *request)
> >> +{
> >> + CompressData *cd = request;
> >> + RAMState *rs = ram_state;
> >> + int bytes_xmit;
> >> +
> >> + bytes_xmit = qemu_put_qemu_file(rs->f, cd->file);
> >> + update_compress_thread_counts(cd, bytes_xmit);
> >> +}
> >> +
> >> +static const ThreadedWorkqueueOps compress_ops = {
> >> + .thread_request_init = compress_thread_data_init,
> >> + .thread_request_uninit = compress_thread_data_fini,
> >> + .thread_request_handler = compress_thread_data_handler,
> >> + .thread_request_done = compress_thread_data_done,
> >> + .request_size = sizeof(CompressData),
> >> +};
> >> +
> >> +static Threads *compress_threads;
> >> +
> >> static bool save_page_use_compression(RAMState *rs);
> >>
> >> static void flush_compressed_data(RAMState *rs)
> >> {
> >> - int idx, len, thread_count;
> >> -
> >> if (!save_page_use_compression(rs)) {
> >> return;
> >> }
> >> - thread_count = migrate_compress_threads();
> >>
> >> - qemu_mutex_lock(&comp_done_lock);
> >> - for (idx = 0; idx < thread_count; idx++) {
> >> - while (!comp_param[idx].done) {
> >> - qemu_cond_wait(&comp_done_cond, &comp_done_lock);
> >> - }
> >> - }
> >> - qemu_mutex_unlock(&comp_done_lock);
> >> + threaded_workqueue_wait_for_requests(compress_threads);
> >> +}
> >>
> >> - for (idx = 0; idx < thread_count; idx++) {
> >> - qemu_mutex_lock(&comp_param[idx].mutex);
> >> - if (!comp_param[idx].quit) {
> >> - len = qemu_put_qemu_file(rs->f, comp_param[idx].file);
> >> - /*
> >> - * it's safe to fetch zero_page without holding comp_done_lock
> >> - * as there is no further request submitted to the thread,
> >> - * i.e, the thread should be waiting for a request at this point.
> >> - */
> >> - update_compress_thread_counts(&comp_param[idx], len);
> >> - }
> >> - qemu_mutex_unlock(&comp_param[idx].mutex);
> >> +static void compress_threads_save_cleanup(void)
> >> +{
> >> + if (!compress_threads) {
> >> + return;
> >> }
> >> +
> >> + threaded_workqueue_destroy(compress_threads);
> >> + compress_threads = NULL;
> >> }
> >>
> >> -static inline void set_compress_params(CompressParam *param, RAMBlock *block,
> >> - ram_addr_t offset)
> >> +static int compress_threads_save_setup(void)
> >> {
> >> - param->block = block;
> >> - param->offset = offset;
> >> + if (!migrate_use_compression()) {
> >> + return 0;
> >> + }
> >> +
> >> + compress_threads = threaded_workqueue_create("compress",
> >> + migrate_compress_threads(),
> >> + DEFAULT_THREAD_REQUEST_NR, &compress_ops);
> >> + return compress_threads ? 0 : -1;
> >> }
> >>
> >> static int compress_page_with_multi_thread(RAMState *rs, RAMBlock *block,
> >> ram_addr_t offset)
> >> {
> >> - int idx, thread_count, bytes_xmit = -1, pages = -1;
> >> + CompressData *cd;
> >> bool wait = migrate_compress_wait_thread();
> >>
> >> - thread_count = migrate_compress_threads();
> >> - qemu_mutex_lock(&comp_done_lock);
> >> 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;
> >> - update_compress_thread_counts(&comp_param[idx], bytes_xmit);
> >> - break;
> >> + cd = threaded_workqueue_get_request(compress_threads);
> >> + if (!cd) {
> >> + /*
> >> + * 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 (wait) {
> >> + cpu_relax();
> >> + goto retry;
> >
> > Is there nothing better we can use to wait without eating CPU time?
>
> There is a mechanism to wait without eating CPU time in the data
> structure, but it makes sense to busy wait. There are 4 threads in the
> workqueue, so you have to compare 1/4th of the time spent compressing a
> page, with the trip into the kernel to wake you up. You're adding 20%
> CPU usage, but I'm not surprised it's worthwhile.
Hmm OK; in that case it does at least need a comment because it's a bit
odd, and we should watch out how that scales - I guess it's less of
an overhead the more threads you use.
Dave
> Paolo
>
--
Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
