> On 04-Jan-2024, at 6:14 AM, Hao Xiang <hao.xi...@bytedance.com> wrote:
>
> 1. Refactor multifd_send_thread function.
> 2. Implement buffer_is_zero_use_cpu to handle CPU based zero page
> checking.
> 3. Introduce the batch task structure in MultiFDSendParams.
>
> Signed-off-by: Hao Xiang <hao.xi...@bytedance.com>
> ---
> include/qemu/dsa.h | 43 +++++++++++++++++++++++--
> migration/multifd.c | 77 ++++++++++++++++++++++++++++++++++++---------
> migration/multifd.h | 2 ++
> util/dsa.c | 51 +++++++++++++++++++++++++-----
> 4 files changed, 148 insertions(+), 25 deletions(-)
>
> diff --git a/include/qemu/dsa.h b/include/qemu/dsa.h
> index e002652879..fe7772107a 100644
> --- a/include/qemu/dsa.h
> +++ b/include/qemu/dsa.h
> @@ -2,6 +2,7 @@
> #define QEMU_DSA_H
>
> #include "qemu/error-report.h"
> +#include "exec/cpu-common.h"
> #include "qemu/thread.h"
> #include "qemu/queue.h"
>
> @@ -42,6 +43,20 @@ typedef struct dsa_batch_task {
> QSIMPLEQ_ENTRY(dsa_batch_task) entry;
> } dsa_batch_task;
>
> +#endif
> +
> +struct batch_task {
> + /* Address of each pages in pages */
> + ram_addr_t *addr;
> + /* Zero page checking results */
> + bool *results;
> +#ifdef CONFIG_DSA_OPT
> + struct dsa_batch_task *dsa_batch;
> +#endif
> +};
> +
> +#ifdef CONFIG_DSA_OPT
> +
> /**
> * @brief Initializes DSA devices.
> *
> @@ -74,7 +89,7 @@ void dsa_cleanup(void);
> bool dsa_is_running(void);
>
> /**
> - * @brief Initializes a buffer zero batch task.
> + * @brief Initializes a buffer zero DSA batch task.
> *
> * @param task A pointer to the batch task to initialize.
> * @param results A pointer to an array of zero page checking results.
> @@ -102,7 +117,7 @@ void buffer_zero_batch_task_destroy(struct dsa_batch_task
> *task);
> * @return Zero if successful, otherwise non-zero.
> */
> int
> -buffer_is_zero_dsa_batch_async(struct dsa_batch_task *batch_task,
> +buffer_is_zero_dsa_batch_async(struct batch_task *batch_task,
> const void **buf, size_t count, size_t len);
>
> #else
> @@ -128,6 +143,30 @@ static inline void dsa_stop(void) {}
>
> static inline void dsa_cleanup(void) {}
>
> +static inline int
> +buffer_is_zero_dsa_batch_async(struct batch_task *batch_task,
> + const void **buf, size_t count, size_t len)
> +{
> + exit(1);
> +}
> +
> #endif
>
> +/**
> + * @brief Initializes a general buffer zero batch task.
> + *
> + * @param task A pointer to the general batch task to initialize.
> + * @param batch_size The number of zero page checking tasks in the batch.
> + */
> +void
> +batch_task_init(struct batch_task *task, int batch_size);
> +
> +/**
> + * @brief Destroys a general buffer zero batch task.
> + *
> + * @param task A pointer to the general batch task to destroy.
> + */
> +void
> +batch_task_destroy(struct batch_task *task);
> +
> #endif
> diff --git a/migration/multifd.c b/migration/multifd.c
> index eece85569f..e7c549b93e 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -14,6 +14,8 @@
> #include "qemu/cutils.h"
> #include "qemu/rcu.h"
> #include "qemu/cutils.h"
> +#include "qemu/dsa.h"
> +#include "qemu/memalign.h"
> #include "exec/target_page.h"
> #include "sysemu/sysemu.h"
> #include "exec/ramblock.h"
> @@ -574,6 +576,8 @@ void multifd_save_cleanup(void)
> p->name = NULL;
> multifd_pages_clear(p->pages);
> p->pages = NULL;
> + batch_task_destroy(p->batch_task);
> + p->batch_task = NULL;
> p->packet_len = 0;
> g_free(p->packet);
> p->packet = NULL;
> @@ -678,13 +682,66 @@ int multifd_send_sync_main(QEMUFile *f)
> return 0;
> }
>
> +static void set_page(MultiFDSendParams *p, bool zero_page, uint64_t offset)
> +{
> + RAMBlock *rb = p->pages->block;
> + if (zero_page) {
> + p->zero[p->zero_num] = offset;
> + p->zero_num++;
> + ram_release_page(rb->idstr, offset);
> + } else {
> + p->normal[p->normal_num] = offset;
> + p->normal_num++;
> + }
> +}
> +
> +static void buffer_is_zero_use_cpu(MultiFDSendParams *p)
> +{
> + const void **buf = (const void **)p->batch_task->addr;
> + assert(!migrate_use_main_zero_page());
> +
> + for (int i = 0; i < p->pages->num; i++) {
> + p->batch_task->results[i] = buffer_is_zero(buf[i], p->page_size);
> + }
> +}
> +
> +static void set_normal_pages(MultiFDSendParams *p)
> +{
> + for (int i = 0; i < p->pages->num; i++) {
> + p->batch_task->results[i] = false;
> + }
> +}
Please correct me if I am wrong but set_normal_pages will not be a part of the
final patch, right? They are there for testing out the performance against
different zero page ration scenarios. If it’s so, can we isolate these parts
into a separate patch.
> +
> +static void multifd_zero_page_check(MultiFDSendParams *p)
> +{
> + /* older qemu don't understand zero page on multifd channel */
> + bool use_multifd_zero_page = !migrate_use_main_zero_page();
> +
> + RAMBlock *rb = p->pages->block;
> +
> + for (int i = 0; i < p->pages->num; i++) {
> + p->batch_task->addr[i] = (ram_addr_t)(rb->host +
> p->pages->offset[i]);
> + }
> +
> + if (use_multifd_zero_page) {
> + buffer_is_zero_use_cpu(p);
> + } else {
> + /* No zero page checking. All pages are normal pages. */
> + set_normal_pages(p);
> + }
> +
> + for (int i = 0; i < p->pages->num; i++) {
> + uint64_t offset = p->pages->offset[i];
> + bool zero_page = p->batch_task->results[i];
> + set_page(p, zero_page, offset);
> + }
> +}
> +
> static void *multifd_send_thread(void *opaque)
> {
> MultiFDSendParams *p = opaque;
> MigrationThread *thread = NULL;
> Error *local_err = NULL;
> - /* qemu older than 8.2 don't understand zero page on multifd channel */
> - bool use_multifd_zero_page = !migrate_use_main_zero_page();
> int ret = 0;
> bool use_zero_copy_send = migrate_zero_copy_send();
>
> @@ -710,7 +767,6 @@ static void *multifd_send_thread(void *opaque)
> qemu_mutex_lock(&p->mutex);
>
> if (p->pending_job) {
> - RAMBlock *rb = p->pages->block;
> uint64_t packet_num = p->packet_num;
> uint32_t flags;
>
> @@ -723,18 +779,7 @@ static void *multifd_send_thread(void *opaque)
> p->iovs_num = 1;
> }
>
> - for (int i = 0; i < p->pages->num; i++) {
> - uint64_t offset = p->pages->offset[i];
> - if (use_multifd_zero_page &&
> - buffer_is_zero(rb->host + offset, p->page_size)) {
> - p->zero[p->zero_num] = offset;
> - p->zero_num++;
> - ram_release_page(rb->idstr, offset);
> - } else {
> - p->normal[p->normal_num] = offset;
> - p->normal_num++;
> - }
> - }
> + multifd_zero_page_check(p);
>
> if (p->normal_num) {
> ret = multifd_send_state->ops->send_prepare(p, &local_err);
> @@ -975,6 +1020,8 @@ int multifd_save_setup(Error **errp)
> p->pending_job = 0;
> p->id = i;
> p->pages = multifd_pages_init(page_count);
> + p->batch_task = g_malloc0(sizeof(struct batch_task));
> + batch_task_init(p->batch_task, page_count);
> p->packet_len = sizeof(MultiFDPacket_t)
> + sizeof(uint64_t) * page_count;
> p->packet = g_malloc0(p->packet_len);
> diff --git a/migration/multifd.h b/migration/multifd.h
> index 13762900d4..97b5f888a7 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -119,6 +119,8 @@ typedef struct {
> * pending_job != 0 -> multifd_channel can use it.
> */
> MultiFDPages_t *pages;
> + /* Zero page checking batch task */
> + struct batch_task *batch_task;
>
> /* thread local variables. No locking required */
>
> diff --git a/util/dsa.c b/util/dsa.c
> index 5a2bf33651..f6224a27d4 100644
> --- a/util/dsa.c
> +++ b/util/dsa.c
> @@ -802,7 +802,7 @@ buffer_zero_task_init_int(struct dsa_hw_desc *descriptor,
> }
>
> /**
> - * @brief Initializes a buffer zero batch task.
> + * @brief Initializes a buffer zero DSA batch task.
> *
> * @param task A pointer to the batch task to initialize.
> * @param results A pointer to an array of zero page checking results.
> @@ -1107,29 +1107,64 @@ void dsa_cleanup(void)
> * @return Zero if successful, otherwise non-zero.
> */
> int
> -buffer_is_zero_dsa_batch_async(struct dsa_batch_task *batch_task,
> +buffer_is_zero_dsa_batch_async(struct batch_task *batch_task,
> const void **buf, size_t count, size_t len)
> {
> - if (count <= 0 || count > batch_task->batch_size) {
> + struct dsa_batch_task *dsa_batch = batch_task->dsa_batch;
> +
> + if (count <= 0 || count > dsa_batch->batch_size) {
> return -1;
> }
>
> - assert(batch_task != NULL);
> + assert(dsa_batch != NULL);
> assert(len != 0);
> assert(buf != NULL);
>
> if (count == 1) {
> /* DSA doesn't take batch operation with only 1 task. */
> - buffer_zero_dsa_async(batch_task, buf[0], len);
> + buffer_zero_dsa_async(dsa_batch, buf[0], len);
> } else {
> - buffer_zero_dsa_batch_async(batch_task, buf, count, len);
> + buffer_zero_dsa_batch_async(dsa_batch, buf, count, len);
> }
>
> - buffer_zero_dsa_wait(batch_task);
> - buffer_zero_cpu_fallback(batch_task);
> + buffer_zero_dsa_wait(dsa_batch);
> + buffer_zero_cpu_fallback(dsa_batch);
>
> return 0;
> }
>
> #endif
>
> +/**
> + * @brief Initializes a general buffer zero batch task.
> + *
> + * @param task A pointer to the general batch task to initialize.
> + * @param batch_size The number of zero page checking tasks in the batch.
> + */
> +void
> +batch_task_init(struct batch_task *task, int batch_size)
> +{
> + task->addr = g_new0(ram_addr_t, batch_size);
> + task->results = g_new0(bool, batch_size);
> +#ifdef CONFIG_DSA_OPT
> + task->dsa_batch = qemu_memalign(64, sizeof(struct dsa_batch_task));
> + buffer_zero_batch_task_init(task->dsa_batch, task->results, batch_size);
> +#endif
> +}
> +
> +/**
> + * @brief Destroys a general buffer zero batch task.
> + *
> + * @param task A pointer to the general batch task to destroy.
> + */
> +void
> +batch_task_destroy(struct batch_task *task)
> +{
> + g_free(task->addr);
> + g_free(task->results);
> +#ifdef CONFIG_DSA_OPT
> + buffer_zero_batch_task_destroy(task->dsa_batch);
> + qemu_vfree(task->dsa_batch);
> +#endif
> +}
> +
> --
> 2.30.2
>
>
>
