Yichen Wang <yichen.w...@bytedance.com> writes:
> On Thu, Nov 21, 2024 at 12:52 PM Fabiano Rosas <faro...@suse.de> wrote:
>>
>> Yichen Wang <yichen.w...@bytedance.com> writes:
>>
>> > From: Hao Xiang <hao.xi...@linux.dev>
>> >
>> > Multifd sender path gets an array of pages queued by the migration
>> > thread. It performs zero page checking on every page in the array.
>> > The pages are classfied as either a zero page or a normal page. This
>> > change uses Intel DSA to offload the zero page checking from CPU to
>> > the DSA accelerator. The sender thread submits a batch of pages to DSA
>> > hardware and waits for the DSA completion thread to signal for work
>> > completion.
>> >
>> > Signed-off-by: Hao Xiang <hao.xi...@linux.dev>
>> > Signed-off-by: Yichen Wang <yichen.w...@bytedance.com>
>> > ---
>> > migration/multifd-zero-page.c | 129 ++++++++++++++++++++++++++++++----
>> > migration/multifd.c | 29 +++++++-
>> > migration/multifd.h | 5 ++
>> > 3 files changed, 147 insertions(+), 16 deletions(-)
>> >
>> > diff --git a/migration/multifd-zero-page.c b/migration/multifd-zero-page.c
>> > index f1e988a959..639aed9f6b 100644
>> > --- a/migration/multifd-zero-page.c
>> > +++ b/migration/multifd-zero-page.c
>> > @@ -21,7 +21,9 @@
>> >
>> > static bool multifd_zero_page_enabled(void)
>> > {
>> > - return migrate_zero_page_detection() == ZERO_PAGE_DETECTION_MULTIFD;
>> > + ZeroPageDetection curMethod = migrate_zero_page_detection();
>> > + return (curMethod == ZERO_PAGE_DETECTION_MULTIFD ||
>> > + curMethod == ZERO_PAGE_DETECTION_DSA_ACCEL);
>> > }
>> >
>> > static void swap_page_offset(ram_addr_t *pages_offset, int a, int b)
>> > @@ -37,26 +39,49 @@ static void swap_page_offset(ram_addr_t *pages_offset,
>> > int a, int b)
>> > pages_offset[b] = temp;
>> > }
>> >
>> > +#ifdef CONFIG_DSA_OPT
>> > +
>> > +static void swap_result(bool *results, int a, int b)
>> > +{
>> > + bool temp;
>> > +
>> > + if (a == b) {
>> > + return;
>> > + }
>> > +
>> > + temp = results[a];
>> > + results[a] = results[b];
>> > + results[b] = temp;
>> > +}
>> > +
>> > /**
>> > - * multifd_send_zero_page_detect: Perform zero page detection on all
>> > pages.
>> > + * zero_page_detect_dsa: Perform zero page detection using
>> > + * Intel Data Streaming Accelerator (DSA).
>> > *
>> > - * Sorts normal pages before zero pages in p->pages->offset and updates
>> > - * p->pages->normal_num.
>> > + * Sorts normal pages before zero pages in pages->offset and updates
>> > + * pages->normal_num.
>> > *
>> > * @param p A pointer to the send params.
>> > */
>> > -void multifd_send_zero_page_detect(MultiFDSendParams *p)
>> > +static void zero_page_detect_dsa(MultiFDSendParams *p)
>> > {
>> > MultiFDPages_t *pages = &p->data->u.ram;
>> > RAMBlock *rb = pages->block;
>> > - int i = 0;
>> > - int j = pages->num - 1;
>> > + bool *results = p->dsa_batch_task->results;
>> >
>> > - if (!multifd_zero_page_enabled()) {
>> > - pages->normal_num = pages->num;
>> > - goto out;
>> > + for (int i = 0; i < pages->num; i++) {
>> > + p->dsa_batch_task->addr[i] =
>> > + (ram_addr_t)(rb->host + pages->offset[i]);
>> > }
>> >
>> > + buffer_is_zero_dsa_batch_sync(p->dsa_batch_task,
>> > + (const void **)p->dsa_batch_task->addr,
>> > + pages->num,
>> > + multifd_ram_page_size());
>> > +
>> > + int i = 0;
>> > + int j = pages->num - 1;
>> > +
>> > /*
>> > * Sort the page offset array by moving all normal pages to
>> > * the left and all zero pages to the right of the array.
>> > @@ -64,23 +89,39 @@ void multifd_send_zero_page_detect(MultiFDSendParams
>> > *p)
>> > while (i <= j) {
>> > uint64_t offset = pages->offset[i];
>> >
>> > - if (!buffer_is_zero(rb->host + offset, multifd_ram_page_size())) {
>> > + if (!results[i]) {
>> > i++;
>> > continue;
>> > }
>> >
>> > + swap_result(results, i, j);
>> > swap_page_offset(pages->offset, i, j);
>> > ram_release_page(rb->idstr, offset);
>> > j--;
>> > }
>> >
>> > pages->normal_num = i;
>> > +}
>> >
>> > -out:
>> > - stat64_add(&mig_stats.normal_pages, pages->normal_num);
>> > - stat64_add(&mig_stats.zero_pages, pages->num - pages->normal_num);
>> > +void multifd_dsa_cleanup(void)
>> > +{
>> > + qemu_dsa_cleanup();
>> > +}
>> > +
>> > +#else
>> > +
>> > +static void zero_page_detect_dsa(MultiFDSendParams *p)
>> > +{
>> > + g_assert_not_reached();
>> > +}
>> > +
>> > +void multifd_dsa_cleanup(void)
>> > +{
>> > + return ;
>> > }
>> >
>> > +#endif
>> > +
>> > void multifd_recv_zero_page_process(MultiFDRecvParams *p)
>> > {
>> > for (int i = 0; i < p->zero_num; i++) {
>> > @@ -92,3 +133,63 @@ void multifd_recv_zero_page_process(MultiFDRecvParams
>> > *p)
>> > }
>> > }
>> > }
>> > +
>> > +/**
>> > + * zero_page_detect_cpu: Perform zero page detection using CPU.
>> > + *
>> > + * Sorts normal pages before zero pages in p->pages->offset and updates
>> > + * p->pages->normal_num.
>> > + *
>> > + * @param p A pointer to the send params.
>> > + */
>> > +static void zero_page_detect_cpu(MultiFDSendParams *p)
>> > +{
>> > + MultiFDPages_t *pages = &p->data->u.ram;
>> > + RAMBlock *rb = pages->block;
>> > + int i = 0;
>> > + int j = pages->num - 1;
>> > +
>> > + /*
>> > + * Sort the page offset array by moving all normal pages to
>> > + * the left and all zero pages to the right of the array.
>> > + */
>> > + while (i <= j) {
>> > + uint64_t offset = pages->offset[i];
>> > +
>> > + if (!buffer_is_zero(rb->host + offset, multifd_ram_page_size())) {
>> > + i++;
>> > + continue;
>> > + }
>> > +
>> > + swap_page_offset(pages->offset, i, j);
>> > + ram_release_page(rb->idstr, offset);
>> > + j--;
>> > + }
>> > +
>> > + pages->normal_num = i;
>> > +}
>> > +
>> > +/**
>> > + * multifd_send_zero_page_detect: Perform zero page detection on all
>> > pages.
>> > + *
>> > + * @param p A pointer to the send params.
>> > + */
>> > +void multifd_send_zero_page_detect(MultiFDSendParams *p)
>> > +{
>> > + MultiFDPages_t *pages = &p->data->u.ram;
>> > +
>> > + if (!multifd_zero_page_enabled()) {
>> > + pages->normal_num = pages->num;
>> > + goto out;
>> > + }
>> > +
>> > + if (qemu_dsa_is_running()) {
>> > + zero_page_detect_dsa(p);
>> > + } else {
>> > + zero_page_detect_cpu(p);
>> > + }
>> > +
>> > +out:
>> > + stat64_add(&mig_stats.normal_pages, pages->normal_num);
>> > + stat64_add(&mig_stats.zero_pages, pages->num - pages->normal_num);
>> > +}
>> > diff --git a/migration/multifd.c b/migration/multifd.c
>> > index 4374e14a96..689acceff2 100644
>> > --- a/migration/multifd.c
>> > +++ b/migration/multifd.c
>> > @@ -13,6 +13,7 @@
>> > #include "qemu/osdep.h"
>> > #include "qemu/cutils.h"
>> > #include "qemu/rcu.h"
>> > +#include "qemu/dsa.h"
>> > #include "exec/target_page.h"
>> > #include "sysemu/sysemu.h"
>> > #include "exec/ramblock.h"
>> > @@ -462,6 +463,8 @@ static bool
>> > multifd_send_cleanup_channel(MultiFDSendParams *p, Error **errp)
>> > p->name = NULL;
>> > g_free(p->data);
>> > p->data = NULL;
>> > + buffer_zero_batch_task_destroy(p->dsa_batch_task);
>> > + p->dsa_batch_task = NULL;
>> > p->packet_len = 0;
>> > g_free(p->packet);
>> > p->packet = NULL;
>> > @@ -493,6 +496,8 @@ void multifd_send_shutdown(void)
>> >
>> > multifd_send_terminate_threads();
>> >
>> > + multifd_dsa_cleanup();
>> > +
>> > for (i = 0; i < migrate_multifd_channels(); i++) {
>> > MultiFDSendParams *p = &multifd_send_state->params[i];
>> > Error *local_err = NULL;
>> > @@ -814,11 +819,31 @@ bool multifd_send_setup(void)
>> > uint32_t page_count = multifd_ram_page_count();
>> > bool use_packets = multifd_use_packets();
>> > uint8_t i;
>> > + Error *local_err = NULL;
>> >
>> > if (!migrate_multifd()) {
>> > return true;
>> > }
>> >
>> > + if (s &&
>> > + s->parameters.zero_page_detection ==
>> > ZERO_PAGE_DETECTION_DSA_ACCEL) {
>> > + // Populate the dsa device path from accel-path
>>
>> scripts/checkpatch.pl would have rejected this.
>>
>
> Sorry. I will make sure to run checkpatch.pl, unit test (both
> with/without DSA), before the send-email...
>
>> > + const strList *accel_path = migrate_accel_path();
>> > + g_autofree strList *dsa_parameter = g_malloc0(sizeof(strList));
>> > + strList **tail = &dsa_parameter;
>> > + while (accel_path) {
>> > + if (strncmp(accel_path->value, "dsa:", 4) == 0) {
>> > + QAPI_LIST_APPEND(tail, &accel_path->value[4]);
>> > + }
>> > + accel_path = accel_path->next;
>> > + }
>>
>> The parsing of the parameter should be in options.c. In fact, Peter
>> suggested in v4 to make all of this a multifd_dsa_send_setup() or
>> multifd_dsa_init(), I think that's a good idea.
>>
>
> Will fix it in the next version.
>
>> > + if (qemu_dsa_init(dsa_parameter, &local_err)) {
>> > + ret = -1;
>>
>> migrate_set_error(s, local_err);
>> goto err;
>
> Will fix it in the next version. But here we can't goto err, because
> the cleanup() function will be called when setup() fails, and it has
> assumptions that a certain data structure is in place. If we exit
> earlier, the cleanup() function will complain and fail.
>
Which data structure? Is that multifd_send_state below? You could move
those before qemu_dsa_init if that's the case.
>>
>> > + } else {
>> > + qemu_dsa_start();
>> > + }
>> > + }
>> > +
>> > thread_count = migrate_multifd_channels();
>> > multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
>> > multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
>> > @@ -829,12 +854,12 @@ bool multifd_send_setup(void)
>> >
>> > for (i = 0; i < thread_count; i++) {
>> > MultiFDSendParams *p = &multifd_send_state->params[i];
>> > - Error *local_err = NULL;
>> >
>> > qemu_sem_init(&p->sem, 0);
>> > qemu_sem_init(&p->sem_sync, 0);
>> > p->id = i;
>> > p->data = multifd_send_data_alloc();
>> > + p->dsa_batch_task = buffer_zero_batch_task_init(page_count);
>> >
>> > if (use_packets) {
>> > p->packet_len = sizeof(MultiFDPacket_t)
>> > @@ -865,7 +890,6 @@ bool multifd_send_setup(void)
>> >
>> > for (i = 0; i < thread_count; i++) {
>> > MultiFDSendParams *p = &multifd_send_state->params[i];
>> > - Error *local_err = NULL;
>> >
>> > ret = multifd_send_state->ops->send_setup(p, &local_err);
>> > if (ret) {
>> > @@ -1047,6 +1071,7 @@ void multifd_recv_cleanup(void)
>> > qemu_thread_join(&p->thread);
>> > }
>> > }
>> > + multifd_dsa_cleanup();
>> > for (i = 0; i < migrate_multifd_channels(); i++) {
>> > multifd_recv_cleanup_channel(&multifd_recv_state->params[i]);
>> > }
>> > diff --git a/migration/multifd.h b/migration/multifd.h
>> > index 50d58c0c9c..e293ddbc1d 100644
>> > --- a/migration/multifd.h
>> > +++ b/migration/multifd.h
>> > @@ -15,6 +15,7 @@
>> >
>> > #include "exec/target_page.h"
>> > #include "ram.h"
>> > +#include "qemu/dsa.h"
>> >
>> > typedef struct MultiFDRecvData MultiFDRecvData;
>> > typedef struct MultiFDSendData MultiFDSendData;
>> > @@ -155,6 +156,9 @@ typedef struct {
>> > bool pending_sync;
>> > MultiFDSendData *data;
>> >
>> > + /* Zero page checking batch task */
>> > + QemuDsaBatchTask *dsa_batch_task;
>> > +
>> > /* thread local variables. No locking required */
>> >
>> > /* pointer to the packet */
>> > @@ -313,6 +317,7 @@ void multifd_send_fill_packet(MultiFDSendParams *p);
>> > bool multifd_send_prepare_common(MultiFDSendParams *p);
>> > void multifd_send_zero_page_detect(MultiFDSendParams *p);
>> > void multifd_recv_zero_page_process(MultiFDRecvParams *p);
>> > +void multifd_dsa_cleanup(void);
>> >
>> > static inline void multifd_send_prepare_header(MultiFDSendParams *p)
>> > {
