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>
> ---
> include/qemu/dsa.h | 4 +-
This patch should have no changes to dsa code. Put them in the patches
that introduce them.
> migration/migration.c | 2 +-
> migration/multifd-zero-page.c | 100 ++++++++++++++++++++++++++++++++--
> migration/multifd.c | 43 ++++++++++++++-
> migration/multifd.h | 2 +-
> util/dsa.c | 23 ++++----
Same with these.
> 6 files changed, 150 insertions(+), 24 deletions(-)
>
> diff --git a/include/qemu/dsa.h b/include/qemu/dsa.h
> index fd0305a7c7..a3b502ee41 100644
> --- a/include/qemu/dsa.h
> +++ b/include/qemu/dsa.h
> @@ -83,7 +83,7 @@ typedef struct QemuDsaBatchTask {
> *
> * @return int Zero if successful, otherwise non zero.
> */
> -int qemu_dsa_init(const char *dsa_parameter, Error **errp);
> +int qemu_dsa_init(const strList *dsa_parameter, Error **errp);
>
> /**
> * @brief Start logic to enable using DSA.
> @@ -146,7 +146,7 @@ static inline bool qemu_dsa_is_running(void)
> return false;
> }
>
> -static inline int qemu_dsa_init(const char *dsa_parameter, Error **errp)
> +static inline int qemu_dsa_init(const strList *dsa_parameter, Error **errp)
> {
> error_setg(errp, "DSA accelerator is not enabled.");
> return -1;
> diff --git a/migration/migration.c b/migration/migration.c
> index 3dea06d577..085395b900 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -3469,7 +3469,7 @@ static void *migration_thread(void *opaque)
> object_ref(OBJECT(s));
> update_iteration_initial_status(s);
>
> - if (!multifd_send_setup()) {
> + if (!multifd_send_setup(&local_err)) {
This is interesting, probably more correct than what we're doing
today. But you need to hoist the error handling out of
multifd_send_setup into here. And put this in a separate patch because
it is an improvement on its own.
> goto out;
> }
>
> diff --git a/migration/multifd-zero-page.c b/migration/multifd-zero-page.c
The way git generated this diff makes it hard to review. When this
happens, you can use a different algorithm such as --patience when
generating the patches. Compare git show vs. git show --patience to see
the difference.
> index e1b8370f88..ffb5611d44 100644
> --- a/migration/multifd-zero-page.c
> +++ b/migration/multifd-zero-page.c
> @@ -37,25 +37,84 @@ static void swap_page_offset(ram_addr_t *pages_offset,
> int a, int b)
> }
>
> /**
> - * multifd_send_zero_page_detect: Perform zero page detection on all pages.
> + * 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.
Probably best to carry this part along as well. This is the public
function that people will most likely look at first.
> *
> * @param p A pointer to the send params.
> */
> -void multifd_send_zero_page_detect(MultiFDSendParams *p)
> +static void zero_page_detect_cpu(MultiFDSendParams *p)
> {
> MultiFDPages_t *pages = p->pages;
> RAMBlock *rb = pages->block;
> int i = 0;
> int j = pages->num - 1;
>
> - if (!multifd_zero_page_enabled()) {
> - pages->normal_num = pages->num;
> + /*
> + * 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, p->page_size)) {
> + i++;
> + continue;
> + }
> +
> + swap_page_offset(pages->offset, i, j);
> + ram_release_page(rb->idstr, offset);
> + j--;
> + }
> +
> + pages->normal_num = i;
> +}
> +
> +
> +#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;
> +}
> +
> +/**
> + * 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.
> + *
> + * @param p A pointer to the send params.
> + */
> +static void zero_page_detect_dsa(MultiFDSendParams *p)
> +{
> + MultiFDPages_t *pages = p->pages;
Actually use the pages variable all over instead of dereferencing
p->pages again.
> + RAMBlock *rb = pages->block;
> + bool *results = p->dsa_batch_task->results;
I think we had a suggestion from Peter to not carry the batch task in
the channel parameters, no?
> +
> + for (int i = 0; i < p->pages->num; i++) {
> + p->dsa_batch_task->addr[i] =
> + (ram_addr_t)(rb->host + p->pages->offset[i]);
> + }
> +
> + buffer_is_zero_dsa_batch_sync(p->dsa_batch_task,
> + (const void **)p->dsa_batch_task->addr,
> + p->pages->num,
> + p->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.
> @@ -63,11 +122,12 @@ void multifd_send_zero_page_detect(MultiFDSendParams *p)
> while (i <= j) {
> uint64_t offset = pages->offset[i];
>
> - if (!buffer_is_zero(rb->host + offset, p->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--;
> @@ -76,6 +136,15 @@ void multifd_send_zero_page_detect(MultiFDSendParams *p)
> pages->normal_num = i;
> }
>
> +#else
> +
> +static void zero_page_detect_dsa(MultiFDSendParams *p)
> +{
> + exit(1);
g_assert_not_reached();
> +}
> +
> +#endif
> +
> void multifd_recv_zero_page_process(MultiFDRecvParams *p)
> {
> for (int i = 0; i < p->zero_num; i++) {
> @@ -87,3 +156,24 @@ void multifd_recv_zero_page_process(MultiFDRecvParams *p)
> }
> }
> }
> +
> +/**
> + * 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->pages;
> +
> + if (!multifd_zero_page_enabled()) {
> + pages->normal_num = pages->num;
> + return;
> + }
> +
> + if (qemu_dsa_is_running()) {
> + zero_page_detect_dsa(p);
> + } else {
> + zero_page_detect_cpu(p);
> + }
> +}
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 6f8edd4b6a..014fee757a 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -817,6 +817,32 @@ static void multifd_send_cleanup_state(void)
> multifd_send_state = NULL;
> }
>
> +static bool multifd_dsa_setup(MigrationState *s, const char *role, Error
> **errp)
You don't need MigrationState here. You can call the function only from
multifd_send_setup() and use migrate_zero_page_detection() to check for
DSA.
> +{
> + /*
> + * Only setup DSA when needed. Currently, DSA is only used for zero page
> + * detection, which is only needed on sender side.
> + */
> + if (!s ||
> + s->parameters.zero_page_detection != ZERO_PAGE_DETECTION_DSA_ACCEL) {
> + return true;
> + }
> +
> + const strList *dsa_parameter = migrate_dsa_accel_path();
> + if (qemu_dsa_init(dsa_parameter, errp)) {
> + error_setg(errp, "multifd: %s failed to initialize DSA.", role);
> + return false;
> + }
> + qemu_dsa_start();
> +
> + return true;
> +}
> +
> +static void multifd_dsa_cleanup(void)
> +{
> + qemu_dsa_cleanup();
> +}
Hmm, these two functions seem to fit better in multifd-zero-page.c.
> +
> void multifd_send_shutdown(void)
> {
> int i;
> @@ -827,6 +853,8 @@ 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;
> @@ -1156,7 +1184,7 @@ static bool multifd_new_send_channel_create(gpointer
> opaque, Error **errp)
> return true;
> }
>
> -bool multifd_send_setup(void)
> +bool multifd_send_setup(Error **errp)
> {
> MigrationState *s = migrate_get_current();
> Error *local_err = NULL;
Remove this and use errp instead everywhere.
> @@ -1169,6 +1197,10 @@ bool multifd_send_setup(void)
> return true;
> }
>
> + if (!multifd_dsa_setup(s, "Sender", errp)) {
> + return false;
> + }
> +
> thread_count = migrate_multifd_channels();
> multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
> multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
> @@ -1395,6 +1427,7 @@ 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]);
> }
> @@ -1570,6 +1603,7 @@ int multifd_recv_setup(Error **errp)
> uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
> bool use_packets = multifd_use_packets();
> uint8_t i;
> + int ret;
>
> /*
> * Return successfully if multiFD recv state is already initialised
> @@ -1579,6 +1613,10 @@ int multifd_recv_setup(Error **errp)
> return 0;
> }
>
> + if (!multifd_dsa_setup(NULL, "Receiver", errp)) {
> + return -1;
> + }
Is there a reason to call this here?
> +
> thread_count = migrate_multifd_channels();
> multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
> multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
> @@ -1617,13 +1655,12 @@ int multifd_recv_setup(Error **errp)
>
> for (i = 0; i < thread_count; i++) {
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
> - int ret;
> -
This is a separate cleanup patch.
> ret = multifd_recv_state->ops->recv_setup(p, errp);
> if (ret) {
> return ret;
> }
> }
> +
Avoid introducing extra lines for no reason, this leads to git conflicts
sometimes.
> return 0;
> }
>
> diff --git a/migration/multifd.h b/migration/multifd.h
> index 027f57bf4e..871e3aa063 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -18,7 +18,7 @@
>
> typedef struct MultiFDRecvData MultiFDRecvData;
>
> -bool multifd_send_setup(void);
> +bool multifd_send_setup(Error **errp);
> void multifd_send_shutdown(void);
> void multifd_send_channel_created(void);
> int multifd_recv_setup(Error **errp);
> diff --git a/util/dsa.c b/util/dsa.c
> index 5aba1ae23a..44b1130a51 100644
> --- a/util/dsa.c
> +++ b/util/dsa.c
> @@ -116,27 +116,27 @@ dsa_device_cleanup(QemuDsaDevice *instance)
> */
> static int
> dsa_device_group_init(QemuDsaDeviceGroup *group,
> - const char *dsa_parameter,
> + const strList *dsa_parameter,
> Error **errp)
> {
> - if (dsa_parameter == NULL || strlen(dsa_parameter) == 0) {
> - return 0;
> + if (dsa_parameter == NULL) {
> + /* HACKING ALERT. */
> + /* return 0; */
> + dsa_parameter = &(strList) {
> + .value = (char *)"/dev/dsa/wq0.0", .next = NULL
> + };
> }
>
> int ret = 0;
> - char *local_dsa_parameter = g_strdup(dsa_parameter);
> const char *dsa_path[MAX_DSA_DEVICES];
> int num_dsa_devices = 0;
> - char delim[2] = " ";
>
> - char *current_dsa_path = strtok(local_dsa_parameter, delim);
> -
> - while (current_dsa_path != NULL) {
> - dsa_path[num_dsa_devices++] = current_dsa_path;
> + while (dsa_parameter) {
> + dsa_path[num_dsa_devices++] = dsa_parameter->value;
> if (num_dsa_devices == MAX_DSA_DEVICES) {
> break;
> }
> - current_dsa_path = strtok(NULL, delim);
> + dsa_parameter = dsa_parameter->next;
> }
>
> group->dsa_devices =
> @@ -161,7 +161,6 @@ dsa_device_group_init(QemuDsaDeviceGroup *group,
> }
>
> exit:
> - g_free(local_dsa_parameter);
> return ret;
> }
>
> @@ -718,7 +717,7 @@ dsa_globals_init(void)
> *
> * @return int Zero if successful, otherwise non zero.
> */
> -int qemu_dsa_init(const char *dsa_parameter, Error **errp)
> +int qemu_dsa_init(const strList *dsa_parameter, Error **errp)
> {
> dsa_globals_init();
